1, dietary factors High-fat, high-meat, low-fiber diet High-fat diet can significantly increase the concentration of neutral cholesterol and bile acids in the colon, both of which have a similar stereo structure to carcinogenic polycyclic aromatic hydrocarbons, and their degradation products also have carcinogenic or adjuvant carcinogenic effects. And fiber can absorb water, so it increases the amount of stool, shortens its residence time in the intestine, adsorbs harmful substances, and promotes discharge. Suggestion: adjust the diet structure: reduce fatty protein high energy intake, increase fruits, vegetables and dietary fiber. Active exercise: obesity, especially abdominal obesity, caused by excessive intake of high-fat and high-meat foods, and low physical activity are also risk factors for colorectal cancer. Active exercise and reducing obesity can play a role in preventing colorectal cancer. 2.Genetic factors Family members with family history of colorectal cancer have 2-6 times higher risk of colorectal cancer than the general population. 15% of colorectal cancer patients have clear family history. Recommendation: For those who have a family history of colorectal cancer, screening high-risk groups through genetic examination and regular colonoscopy is an important aspect of colorectal cancer prevention. 3.Colorectal polyps The incidence of colorectal cancer is about 5 times higher in those with colorectal polyps than in those without colorectal polyps. Hereditary familial polyposis is closely related to colorectal cancer, of which more than 80% of patients may develop into colorectal cancer after the age of 50. Suggestions: For those who have colorectal polyps should actively undergo electrodesiccation treatment as early as possible, and regular review. Chronic inflammatory stimulation Chronic bacterial dysentery, chronic amoebic enteropathy and Crohn’s disease have a higher incidence of colorectal cancer than the control population of the same age. The incidence of colorectal cancer in ulcerative colitis is 5 to 10 times higher than that of normal population. As chronic inflammation can cause intestinal mucosa exudation and edema, repeated destruction and repair process can lead to fibrous tissue proliferation, epithelial cell interstitial changes, forming multiple polyps and chronic granulomas, and then cancer. Suggestion: actively treat primary diseases such as ulcerative colitis to reduce inflammatory stimulation and decrease the incidence of colorectal cancer.