After radical resection of colorectal cancer, even with adjuvant radiotherapy, there is still a possibility of recurrence and metastasis to distant organs such as liver, lung and bone, so patients should be closely followed up. It is recommended to test: 1) serum tumor markers such as carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) every 2-3 months for 2 years after surgery; 2) complete blood count, liver and kidney function tests; 3) chest X-ray; 4) liver ultrasound If the above tests reveal clues of recurrence or metastasis, enhanced CT scan of chest, abdomen and pelvis and colonoscopy will be performed. Every 6 to 12 months: e-colonoscopy. After 2 years, every 6-12 months: 1. serum tumor markers such as carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP); 2. complete blood count, liver and kidney function tests; 3. chest X-ray; 4. liver ultrasound If the above tests reveal clues of recurrence or metastasis, enhanced CT scans of the chest, abdomen and pelvis and colonoscopy will be performed. One e-colonoscopy was performed annually for 5 years.