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 scans of the chest, abdomen and pelvis and colonoscopy will be performed. Every 6-12 months: e-colonoscopy Every 6-12 months after 2 years 1. serum tumor markers such as carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), etc.; 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 a total of 5 years.