γγThe early symptoms of colon cancer are not obvious, and those who have any of the following manifestations over 40 years old should be listed as high-risk group: 1.colon cancer patients in first-degree relatives; 2.history of cancer or history of intestinal adenoma or polyps; 3.positive stool occult blood test; 4.more than two of the following five manifestations: mucus and blood stool, chronic diarrhea, chronic constipation, history of chronic appendicitis and history of mental trauma. If colon cancer is suspected, barium enema or dual gas-barium imaging and fiberoptic colonoscopy will be performed, and it is not difficult to diagnose. Ultrasound and abdominal CT scan are helpful to understand the abdominal mass and enlarged lymph nodes, and to find out whether there is metastasis in the liver. Elevated serum carcinoembryonic antigen (CEA) value has certain significance in suggesting colon cancer, but its specificity is not high. It is mostly used to judge the prognosis and recurrence after surgery.γγ5.Electron colonoscopy is important for diagnosis.