The American Cancer Society considers high-risk groups to be judged by both family history and personal history. The former includes a history of colon or rectal cancer in 1st to 2nd degree relatives, a history of adenomatous polyposis in 1st degree relatives under 60 years of age and a history of familial hereditary syndromes, mainly including familial adenomatous polyposis (FAP), hereditary non-polyp colorectal cancer (HNPCC), Turcot syndrome, Oldfield syndrome and juvenile polyposis; the latter includes a history of inflammatory bowel disease, a The latter includes a history of inflammatory bowel disease, adenomatous polyps and a history of previous cancers of the intestine, adenomas or other organs (breast, ovary, uterus and urinary system). In China, there is no uniform standard for high-risk groups of colon and rectal cancer. Generally, one of the following is considered to be a high-risk group: 1. 30-40 years old or above with gastrointestinal symptoms (especially blood in stool, frequent stools, mucus stools and abdominal pain); 2. Those with family history of colorectal cancer, family history of polyps and hereditary colon disease; 6. Those with history of pelvic radiotherapy; 7. Those with history of gallbladder or appendectomy. For people over 40 years old, those who have one of the following four items can be considered as high-risk candidates for regular colonoscopy screening: 1. positive immunoassay fecal occult blood test (FOBT); 2. history of colon or rectal cancer in first-degree relatives; 3. previous history of cancer or intestinal polyps; 4. two or more of the following: chronic diarrhea, chronic constipation, mucus blood stool, chronic appendicitis and history of mental stimulation.