The cause of colorectal cancer is still unclear, but it may be related to the following factors: 1. Genetic factors It is estimated that genetic factors may play an important role in about 20% of colorectal cancer patients. Family heredity is more common in colon cancer than rectal cancer. 2.Dietary factors It is generally believed that high animal protein, high fat and low fiber diet are the factors of high incidence of colorectal cancer. 3.Disease factors Non-cancerous colorectal disorders such as chronic ulcerative colitis, polyposis, adenoma, etc. It is estimated that 3%-5% of ulcerative colitis occur as colorectal cancer. 4.Other factors such as environmental factors, lifestyle, obesity, stool habits, stool volume, etc.