Nowadays, with the change of lifestyle or diet, the clinical trend of colorectal cancer in China is that the incidence rate is getting higher and the age of incidence is getting younger. Since colorectal cancer is not obvious in early symptoms, many patients have already developed to middle and late stages when diagnosed, losing the best time for treatment. Colorectal cancer is not scary, but the key is early diagnosis and early treatment! Colonoscopy is very important for early detection of colorectal cancer and other intestinal diseases. So, who should do colonoscopy? 1. These people are the high-risk group of colorectal cancer: Family history: those who have family members who have suffered from gastrointestinal cancer, especially those who have colorectal cancer patients in their immediate family, belong to the high-risk group of colorectal cancer. Lifestyle: long-term high protein, high fat, low fiber diet and lack of physical exercise will increase the incidence of colorectal cancer. Inflammatory bowel disease: Patients with chronic intestinal inflammatory diseases such as ulcerative colitis belong to the high-risk group for colorectal cancer. 2. Screening recommendations for high-risk groups: It is recommended to start screening for colorectal cancer at the age of 40, and to review the screening once every 3 to 5 years on average. If colorectal adenomas or polyps with malignant potential are found, they should be removed promptly and reviewed annually for 3 consecutive years, and then every 3 to 5 years. 3.Recommendations for non-high-risk groups: It is recommended that all people over the age of 50 should have a colonoscopy, and if no problems are found, a colonoscopy can be performed every 10 years or so thereafter. If polyps are found during the examination, you should insist on annual re-examination for the first 3 years after removal.