The occurrence of colorectal cancer is closely related to the diet with more fat and less fiber, such as excessive animal fat and animal protein diet, lack of fresh vegetables and fiber food; lack of moderate physical activity. The incidence rate of colorectal cancer is much lower among people who often eat coarse fiber food than those who have high fat, high animal protein and low vegetable diet. Genetic factors are one of the causes of colorectal cancer. Family history: If the first-degree relatives have had colorectal cancer, their next generation will suffer from this disease more than the general population in their lifetime. About 1/4 of the new patients have a family history of colorectal cancer. Inflammatory bowel disease Ulcerative colitis patients have a much higher rate of colorectal cancer than the general population, mostly in patients with extensive lesions from early childhood, and cancer often occurs in the flat mucosa. The development of proliferative lesions of inflammation can often be accompanied by polyp formation and further development of intestinal cancer. In Crohn’s disease (Crohn’s), those with colon and rectal involvement can also cause carcinoma. The chance of developing Crohn’s disease or ulcerative colitis is 30 times higher than that of normal people. In the past, chronic schistosomiasis patients were believed to have chronic ulcers and inflammatory polyps in the colonic mucosa due to the deposition of schistosome eggs and toxin stimulation in the intestinal wall, which can lead to cancer. Most colorectal cancers develop from small precancerous lesions, and the main cause of the development is bad polyps. Among them, villous adenoma-like polyps are more likely to develop into cancer, and the incidence of cancer is about 25%; tubular adenoma-like polyps have a malignancy rate of about 3%.