Rectal cancer is one of the common malignant tumors in clinical practice, and surgical resection is still an important means of treating rectal cancer. Half a century after the introduction of Miles surgery, people began to pay attention to the fact that the surgery requires a permanent abdominal colostomy, which brings mental pressure and inconvenience to patients’ life and social life. In recent years, with the development of national economy and the continuous improvement of people’s living standard, people pay more and more attention to the requirement of good physiological function and quality of life while preserving life. With the in-depth research and exploration on the anatomy, pathology, biological characteristics and lymph node metastasis of rectal cancer, new theories, new views and new surgical procedures have been proposed, so that the number of radical rectal cancer surgery to preserve the function of anal sphincter has been increasing year by year, and the anal preservation procedure accounts for about 70%. Given that there are many types of anus-preserving surgery, how to choose the correct one to achieve the best curative effect has become a hot spot for research. However, while improving the physiological function and quality of life of patients and avoiding colostomy to preserve anus, we must pay attention to reducing the local recurrence rate and improving the five-year survival rate, which is the ultimate goal of surgical treatment. I. Principles to be followed in the selection of anal preservation surgery for rectal cancer Anal preservation surgery for rectal cancer must follow the general principles: first, complete resection and radical treatment of tumor, and second, preservation of function. Emphasize complete resection of tumor, radical lymph node dissection, resection of the lower edge of the cancer foci after rectal free more than 2cm, tumor-free operation techniques during surgery to reduce cancer cell shedding and planting to reduce the local recurrence rate after surgery and improve the 5-year survival rate. Emphasis is placed on preserving the normal defecation control function of the anus in order to improve patients’ postoperative quality of life. Normal defecation function relies on sound sphincter function and complete sensory reflex function, both of which are indispensable, otherwise the anus loses its meaning even if it is preserved. The principle of total rectal mesenteric excision (TME) is emphasized. The technique requires sharp separation under direct vision along the loose natural gap between the pelvic fascia and the wall, complete removal of lymph, blood vessels, fat and fibrous connective tissue around the rectum, and the length of distal mesenteric excision is 5CM from the tumor edge and the distal rectal wall cutting edge is more than 2CM, in order to achieve the thoroughness of tumor excision and radical lymphatic clearance, and to reduce the local recurrence of postoperative surgery. To reduce the local recurrence rate of pelvic cavity after surgery. The correct and reasonable selection of surgical indications is emphasized. Anal conserving surgery cannot be based on individual subjective will, but must pay attention to objective conditions and individualized selection according to the specific conditions of each individual. In recent years, from the development of basic, anatomical, clinical and anastomotic device research, various new anus-preserving surgical procedures have emerged, but only the correct and reasonable selection of surgical procedures can achieve the best efficacy. The concept of surgical treatment of rectal cancer from the initial pure pursuit of the completeness of surgical resection has changed, and anal preservation surgery has reached 70% in larger hospitals, and the principle refers to low rectal cancer within 6CM from the dentate line. Currently, the commonly used anus-preserving surgery includes, (1) low anterior rectal resection, the most commonly used in clinical practice is Dixon surgery. After this operation, most patients can maintain normal defecation and venting functions, which is considered to be a more ideal operation. This procedure is suitable for upper or middle rectal cancer. (2) Transabdominal rectal drag-out resection anastomosis: the common clinical procedure is the Bacon procedure which has been modified in recent years. However, because the function of the anal sphincter is not very satisfactory after the operation, the stool control function is poor, and there are many complications, so the operation is limited. (3) Coloanal anastomosis with the Parks procedure: This procedure replaces the Dixon procedure, but the Parks procedure leads to a drastic reduction in stool storage function, resulting in poor control of early defecation and often requires a colostomy to prevent anastomotic fistula. (4) Pare procedure with intracolonic pouch-anal tube anastomosis: replaces the Parks procedure with colonic-anal tube anastomosis, improves postoperative fecal storage function, and allows rapid return to normal defecation function. (5) Double anastomosis method: The use of double anastomosis can be successfully completed for some ultra-low resection anastomosis that is difficult to achieve with low-level manual sutures, and the surgical operation is more precise and fast, safer and more reliable, especially for difficult exposure, narrow surgical field, and difficult anastomosis becomes simpler and more time-saving, and the anastomotic leak occurred after surgery is 3.4%, which is much lower than that of 10% with surgical sutures. (6) Triple anastomosis method: that is, on the basis of the double anastomosis with a linear cutting anastomosis, complete colonic storage pouch forming, and then the storage pouch anal canal anastomosis, so that the bowel control function is significantly improved, improving the quality of life. (7) In recent years, the introduction of Kaito cutting and suturing device has made it possible to preserve the anus of rectal cancer in a more ultra-low position, and complete the distal rectal closure and cutting in one time, which is more convenient, time-saving and provides a new weapon for the preservation of anus of ultra-low rectal cancer. (8) Transanal ramus resection: it is suitable for early rectal cancer such as tubular adenoma and choroidal tubular adenoma with satisfactory results. (9) Transanal ramus resection for radical rectal cancer: it is suitable for early rectal cancer (T1T2) within 2CMD from the dentate line, and can achieve complete resection of the tumor and obtain satisfactory defecation control function (10) laparoscopic rectal cancer resection and anal preservation: this method was carried out in the mid-1990s, and the most important feature is that it provides surgeons with satisfactory operation space with minimal surgical incisions, and has the advantages of small trauma and quick recovery. It has the advantages of small trauma and quick recovery, and has been gradually carried out in recent years, and its effect is under observation. (11) Li Shiyang et al.’s sleeve-in colorectal mucosal anastomosis: this procedure can preserve the integrity of the anorectal ring and the skin of the anorectal canal, which can significantly improve the function of bowel control after surgery, and at the same time avoid the routine making of temporary abdominal colostomy in Parks surgery, which improves the quality of life of patients and avoids the occurrence of anastomotic leakage and stenosis. The local recurrence rate was 3.7%, with a good outcome. In terms of overall anal preservation surgery, physiological function and quality of life were significantly better than Miles surgery. The efficacy of anus-preserving surgery is slightly higher for early anus-preserving surgery with an overall local recurrence rate of approximately between 10-15%. In recent years, most scholars have improved the surgical style and standardized the procedure, which has significantly decreased the local recurrence rate after anus-preserving surgery. The total postoperative local recurrence rate is between 3-6%. It is well known that while pursuing the thoroughness of surgery to improve the surgical efficacy, it is important to pay more attention to the preservation of function to improve the quality of life of patients. With the improvement of people’s living standard, while the cancer is completely removed to preserve life, higher requirements for postoperative physiological function and quality of life have been put forward. Radical resection of rectal cancer can achieve the principle of three reservations as far as possible. That is, preservation of anal defecation control function, preservation of urinary function and preservation of sexual function has become the hot spot of rectal cancer surgery research at present. At the same time of complete resection of rectal cancer patients to achieve radical cure, the anal bowel control function should be preserved as much as possible to improve patients’ quality of life. The principles of selection are [8]: resection of rectal cancer with lower margin greater than 2 cm; resection of hypofractionated or mucinous adenocarcinoma with lower margin greater than 3 cm; resection of tubular adenoma and villous tubular adenoma with lower margin greater than 1 cm; resection of rectum without cancer cell infiltration in perirectal tissues, especially if the prostate, posterior vaginal wall and bladder are not invaded; resection of liver metastasis with local lesions that can be radically resected; resection of rectal cancer when the cancer tumor When the cancer invades the anal sphincter, the tumor infiltrates and fixes the pelvic cavity and spreads to the adjacent organs, such as the prostate, bladder and vagina, etc., it should be listed as an absolute contraindication to rectal cancer anal preservation surgery. The most common problem of anal bowel control dysfunction in the early stage after rectal cancer anal preservation surgery. The reasons for this are the removal of the rectal storage potbelly, the injury of the nerve return system in the rectal area, and the short time injury to the anal ragus muscle. Therefore, reconstruction of the rectal storage pouch is very important to improve the anal bowel control function after rectal cancer preservation surgery. At present, there are two types of procedures in common use. The J-shaped pouch of the colon uses a J-shaped pouch with a lack of dipping and lifting of the ampulla, and the end-to-end anastomosis between the tip of the pouch and the distal rectum is completed with an anastomosis. For colonic pouchplasty, the distal end of the colon is sutured 3-4 cm away from the distal end of the colon to the proximal end of the colon at 8 cm, and then sutured transversely, and the end of the colon is anastomosed with the stump of the rectum using an anastomosis. As a whole, colonic J-shaped storage pouch and colonic formation storage pouch have similar effects in improving anal bowel control function after rectal cancer preservation surgery. The choice should be based on the individual patient’s situation, and those with relatively long colon should choose colon J-type storage bag, while those with relatively short colon should choose colonic pouch formation, but the length of formed storage bag is generally 5CM, to avoid postoperative pouchitis and emptying disorder. As early as in the 1990s, Japanese scholars actively advocated that lateral lymph node dissection should be done during radical resection of rectal cancer. However, most of the scholars in western countries are against it because of the high surgical trauma, bleeding, long operation time and high morbidity rate. However, the disadvantage is that damage to the autonomic nerves leads to urinary and sexual dysfunction, which significantly reduces the patient’s quality of life. According to the literature, lateral lymph node dissection can reduce the pelvic recurrence rate after surgery for lower and middle rectal cancer. Given that the incidence of urinary dysfunction after conventional radical rectal cancer surgery is as high as 70%, complete or partial erectile dysfunction occurs in 25%-100% of male patients, and loss of ejaculatory function reaches 19%-59% . In recent years, most scholars have conducted in-depth studies on the distribution of autonomic nerve initiation in rectal and pelvic anatomy and proposed a new concept of preserving the autonomic nerve. While ensuring radical resection of the cancer, the autonomic nerve is preserved to achieve preservation of urinary and sexual function. While doing lateral lymph node dissection while preserving the pelvic autonomic nerve according to the extent of lymph node metastasis and infiltration, we can choose to completely preserve the pelvic autonomic nerve and partially preserve the pelvic autonomic nerve, and choose different procedures mainly according to the different lymph node invasion sites, such as preserving the unilateral autonomic nerve, preserving the pelvic visceral nerve, and preserving the sacral 4 pelvic visceral nerve. This can effectively preserve the voiding function and sexual function, which can significantly reduce the incidence of postoperative complications. The total postoperative voiding dysfunction decreased from 65%, to 16%, erectile function increased from 34% to 92%, and ejaculation increased from 0% to 83%, which significantly improved the voiding function and sexual function and improved the postoperative physiological quality of patients. Therefore, the surgery of preserving the autonomic nerve as much as possible during radical resection of rectal cancer has attracted attention and been carried out one after another. In recent years, the progress of preoperative neoadjuvant radiotherapy or catheter-based local infusion chemotherapy has made it possible for those who cannot be resected and cannot preserve the anus in preoperative rectal cancer T3 or T4 stage tumors. Clinical practice has confirmed that preoperative neoadjuvant radiotherapy or catheterized local irrigation chemotherapy can shrink tumors and some of them disappear to reach the descending stage, which can significantly improve the tumor resection rate and anus preservation rate. Professor Yu Baoming reported a group of 30 cases of T3 and T4 rectal cancer, using capecitabine and radiotherapy of 40Gy, and the preoperative evaluation by WHO standard, 73.3% of the masses shrunk and reached the descending stage, 26.7% of the patients reached complete remission, 80% (24/30) of the patients successfully completed anus preservation surgery, and 6 cases performed MILES surgery, this result has changed the traditional concept and contributed to the improvement of resection rate and anus preservation rate. This result is encouraging and demonstrates the great clinical value of preoperative neoadjuvant radiotherapy. The advantage of preoperative radiotherapy is that it can convert most unresectable rectal cancers into resectable ones, and 13-20% of the tumor bodies and symptoms disappear completely, and the preoperative anus-preserving cases are treated with anus-preserving surgery. The radiation dose is generally 40-45 GY, and the timing of surgery after radiotherapy is chosen. Because the time is too short for tumor shrinkage is not obvious, the inflammatory reaction of radiation around rectum is heavy, the resectable rate is relatively low, and the incidence of anastomotic leakage is also high, therefore, in principle, it is more appropriate to rest about 6 weeks after neoadjuvant radiotherapy and chemotherapy before surgery. In today’s radical surgery for rectal cancer, Miles surgery has become the last surgical option, and various anal preservation surgeries are in the prevalent period, so we insist on correct selection of indications and reasonable selection of surgical procedures. Therefore, we should not just subjectively pursue the preservation of the anus and ignore the objective situation of the patient, that is, to achieve radical resection of the tumor and preserve the anus, so that the patient can obtain the physiological function and good quality of life, that is, to reduce the local recurrence rate and improve the 5-year survival rate, which is the goal we finally strive to achieve.