The incidence of colorectal cancer in China is increasing year by year, and there is a trend of youthfulness. At present, whether young people or middle-aged or old people, if patients have blood in stool, mucus stool, unformed stool, frequent bowel movements, long-term abdominal pain or diarrhea, urgency and heaviness, incomplete bowel movement and change in bowel habits, it is recommended to perform colon and rectaloscopy to rule out colorectal cancer. Colorectal cancer and colorectal polyps are both lesions of the intestinal mucosa, which are often found to be in advanced stages by means of ultrasound, CT and MRI. Colon and proctoscopy can detect early intestinal mucosal lesions through direct observation of intestinal mucosa, and biopsy tissue can be taken from suspicious lesions and sent to pathology to observe the specific nature of lesions under the microscope, which is the best choice for screening and diagnosis of chronic enteritis, polyps and early colorectal cancer. Colorectal microscopy gradually tends to become a routine medical examination item, and a large number of screening cases conducted in our hospital this year have identified a part of colorectal cancer patients, as well as many patients with precancerous lesions, and the public has expressed a high opinion of this screening.