In China, 70% of rectal cancers and about the same proportion of villous adenomas are located in the lower rectum, and rectal cancers account for 74% of early colorectal cancers. The main indications for transanal endoscopic microsurgery are adenomas or early rectal cancers within 4-20 cm from the anus, which determines that the development of TEM has a good application prospect in China. Compared with traditional transanal surgery, TEM can reach the middle and upper rectum and lower sigmoid, with clear field exposure, accurate tissue structure recognition and precise resection; compared with transabdominal, trans-sacral (Kraske) and trans-sphincter (York-Mason) surgery, TEM has low complications (5%) and short hospital stay (5.5 days). For rectal tumors up to 10 cm from the anus, they can be removed by transanal surgery. However, for rectal masses around 10 cm, clinical management is quite tricky, and for benign lesions such as polyps of wide base seems to be more than worthwhile, and for suspected cancerous lesions and early rectal cancer, transanal surgery was required in the past, and due to the location, the incidence of anastomotic leakage and other kinds of complications is high, while the theoretical range of TEM is 4-18 cm from the anus, but in fact, through technical adjustment, it can reach 20-25 cm, covering the whole rectum. 25cm, covering the entire rectum and even reach the sigmoid colon, which solves a clinical problem. The main indications for TEM: 1, rectal adenoma or recurrent adenoma, including the non-tip broad-based type and villous adenoma. Generally, the maximum diameter of the tumor occupies within 3/4 circumference of the rectum. 2.T1 stage low risk rectal tumor refers to T1 stage rectal tumor with high or moderate differentiation, small tumor and high activity, and its lymph node metastasis rate is 3%, which has been generally accepted as an indication for TEM. 3.For T2 stage rectal cancer with low risk of recurrence, combined with severe heart disease, chronic obstructive pulmonary disease and other conventional radical surgery risks or refusal of abdominal wall enterostomy, postoperative radiotherapy can be supplemented. 4.Any high risk rectal tumor and stage T3 or above rectal cancer, only as palliative surgery, postoperative radiotherapy and/or chemotherapy must be supplemented. 5.Stenosis of the rectum secondary to anastomosis or anal fistula. 6.Prolapse of the rectum. 7, another part of patients, such as the combination of serious heart disease, chronic obstructive pulmonary disease, such as the risk of conventional radical surgery, can not tolerate radical surgery, TEM is also an option, and then supplemented by chemotherapy after surgery. 8.For some ultra-low rectal cancer, such as early rectal cancer 3-4cm from the anal verge, Miles surgery is needed in the past, if the patient insists to preserve anus and refuses to have abdominal wall enterostomy, TEM can be supplemented with radiotherapy after total resection. 9.Any high risk rectal tumor and stage T3 or above rectal cancer should be treated as palliative surgery only, and postoperative radiotherapy and/or chemotherapy should be used for other aspects such as rectal stricture and rectovaginal leak repair.