1.Eating habits: often consume too much animal fat, such as meat, milk and cheese, etc. Eating too much fat can stimulate excessive bile production, which can produce some wastes after being utilized in the body, and these wastes can cause cancer; the food after barbecue contains carcinogens. 2.Polyps in the intestine and cancer: most of the rectal cancer is caused by cancer on the basis of polyps. Polyp volume increases the cancer rate up to 60%, and the cancer rate of polyps without a tip up to 20%. Therefore, people who suffer from polyps should seek early diagnosis and treatment to prevent cancer. 3.Long-term colorectal inflammation: Patients with long-term inflammation or recurrent colorectal inflammation have a high cancer rate. For example, the cancer rate of those with bleeding ulcerative colorectitis for more than 10 years is 9 times higher than that of normal people. 4.Other factors: such as high incidence of rectal cancer in areas with high incidence of schistosomiasis.