Colorectal cancer is the 4th to 6th most common tumor in China. The age of onset of colorectal cancer in China is around 45 years old, which is 15 years earlier than that in Europe and America. Among young cancer patients in China, colorectal cancer accounts for 23.7%. The development of colorectal cancer has an important relationship with dietary factors, high fat and low fiber are the risk factors of colorectal cancer. High-fat diet increases anaerobic bacteria in stool; lack of fiber in food and decrease in stool volume, then the concentration of carcinogens in the intestine rises leading to the occurrence of cancer. There are several methods of census as follows: 1. Rectal finger examination is the main examination method because 50%-70% of colorectal cancer occurs in the rectum and sigmoid colon. For people over 40 years old, they should be examined once a year, especially those who have abnormal bowel habits such as blood in stool, frequent stool, mucus in stool, and heavy weight after urgency should have rectal finger examination. Rectal finger examination can generally understand the lesions within 5-7 cm from the anus, such as holding the breath and other actions to increase abdominal pressure may find higher parts. 2.Fecal occult blood test is simple, easy and inexpensive, and it can be used once a year for people over 50 years old as a primary screening method for mass screening of colorectal cancer. If it is positive, further colonoscopy will be performed. Stool occult blood test can also detect gastric ulcer, gastric cancer, colorectal polyps and other gastrointestinal disorders, especially the cancer rate of colorectal adenoma can reach 10%-20%. 3, colonoscopy, if possible, from the age of 50 for three consecutive years, once a year. If negative, check once every four years thereafter. Anyone who has blood in stool or change in stool habit and no abnormal finding by rectal finger examination should routinely undergo sigmoidoscopy. About 75% to 80% of rectal and sigmoid colon cancers can be diagnosed by sigmoidoscopy. This kind of examination is simple and can observe the lesions under direct vision, and at the same time can collect biopsy specimens and remove pre-cancerous lesions such as adenomas by electrocautery. In conclusion, if we control cancer patients in primary prevention, we can reduce the occurrence of cancer; if we control cancer patients in secondary prevention, we can reduce the death of cancer patients.