Colonoscopy can detect bowel cancer, and with the improvement of endoscopic treatment and the increase of endoscopic functions, such as endoscopic magnification and electronic staining, colonoscopy can detect early bowel cancer. Endoscopic detection of early stage cancer has been used as a screening target, which is more meaningful than detecting progressive stage cancer. Bowel cancer is a kind of malignant tumor of intestinal mucosa. Middle and late stage bowel cancer is manifested as repeated stool bleeding, and further enlargement of cancer may lead to incomplete bowel obstruction, abdominal pain and other symptoms, and the treatment effect is poor. Therefore, patients are recommended to have regular physical examination to facilitate early detection of the disease.