1. Physical examination: A medical history inquiry and physical examination will be performed once in 3 months, including detailed questioning of recent medical history. For patients with smooth postoperative recovery, recurrence is possible if there is again unexplained weight loss, change in bowel habits again, pelvic pain or perineal inner thigh pain, unexplained irritating cough, abdominal distention and intestinal bleeding. Comprehensive physical examination, check the axillary, supraclavicular and cervical lymph nodes, abdomen mainly check the liver and spleen, whether there is an abdominal mass, anal examination can timely find the recurrence foci in the rectum or pelvis, these physical examination results have certain reference significance for treatment. Although there is still disagreement about the specificity of CEA and whether it can be used as a marker for early diagnosis of recurrence, most scholars believe that elevated CEA in patients with progressive stage and failure to return to normal level after surgery often indicates poor prognosis, and the elevation of CEA often precedes the clinical symptoms of recurrence by 4-5 months. It not only monitors local recurrence but also indicates distant metastases in the liver and lungs. It is ideal to obtain a baseline CEA level before the first surgery, and after radical surgery, the CEA level should return to normal within 2 months. If the CEA level does not drop to normal, it predicts residual tumor. Once the CEA level returns to normal baseline, it should be checked every 3 months. CEA also has some significance in monitoring the efficacy after surgery. If a patient with high CEA value has a decrease in serum CEA value after chemotherapy, it indicates that the tumor is sensitive to chemotherapy drugs. If the serum CEA value continues to remain at a high level, it indicates that chemotherapy is ineffective. The determination of serum CEA should be measured every 4-6 weeks within 2 years after surgery and every 6 months after 2 years. 3.CT or ultrasound examination of abdominal and pelvic cavity: CT examination is applied after colorectal cancer surgery to understand local recurrence and metastases of distant organs (liver, lung, etc.), as well as abdominal and pelvic lymph node metastases with high accuracy, which is now commonly accepted. Under normal circumstances, CT examination should be performed once a year and ultrasound examination once every 6 months. Patients who are eligible should have a CT scan within 4-6 weeks after surgery as a control for later review. The sensitivity of CT to detect pelvic or distant metastases is as high as 88%, but a definitive diagnosis can only be made when the lesion is larger than 1-50 px. Of course, smaller lesions can be detected by comparison with CT films reviewed early after surgery. 4. Chest X-ray: Regular postoperative chest X-ray is necessary. If a suspicious lesion is found, a CT scan of the chest has some value. If the history and physical examination suggest the possibility of bone metastasis, a bone scan should be performed. 5.Colonoscopy or 3D CT examination of the colon: Not only can recurrent anastomotic or heterochronic colorectal adenoma or colorectal cancer be detected, but it also helps to detect adenoma cancer in time. Colonoscopy has special value for observing the anastomosis, and for postoperative anastomotic stricture, it can determine whether it is benign scar or tumor recurrence; if colorectal polyps can be removed by fiberoptic colonoscopy. If a colorectal polyp can be removed by fiberoptic colonoscopy, it should be examined once or more times a year. In summary, the postoperative follow-up program for colorectal cancer patients can be summarized as follows. It should be emphasized that this plan is only a general guideline recommendation, and the clinical application should be individualized according to the patient’s specific condition. Physical examination: every 3 months for 2 years after surgery; every 6 months for 3-5 years; CEA/CA199: if diagnosed or abnormally elevated before surgery, review every 3 months for 2 years and every year for 3-5 years; CT abdomen/pelvis: 4-6 weeks after surgery as a control; review every year for the next 3 years. Ultrasound: every 6 months for 3 years after surgery; intracavitary ultrasound every year after surgery; chest X-ray: every 6 months for 2 years after surgery; every year thereafter; colonoscopy: every year for 2 years after surgery; every 3 years thereafter if both are negative; every year if polyps are found.