Experts point out that early diagnosis of colorectal cancer is difficult and mainly relies on screening and timely diagnosis. The detection rate of stage I colorectal cancer in Europe and America is higher than 20%, but only 9% in Shanghai and even lower in other cities in China. In fact, stage I colorectal cancer is very effective and basically curable, so improving the diagnosis rate of early stage colorectal cancer is the most basic method to improve the treatment effect of colorectal cancer. This year, the colorectal cancer screening for community residents in Shanghai has been officially launched. Services such as colorectal cancer risk assessment, fecal occult blood testing and related prevention and treatment education and consultation will be provided free of charge to the resident population of retirement age and participating in various types of basic medical insurance and basic medical insurance in Shanghai. The program is carried out every three years, with the first round ending at the end of this year, and is initially expected to complete the screening of one million residents.? Experts remind that the criteria for people at high risk of colorectal cancer are: history of colorectal cancer in first-degree relatives; my own history of cancer or intestinal polyps; or those with two or more of the following: chronic diarrhea; chronic constipation; mucus and blood stools; chronic appendicitis; history of mental irritation; and history of chronic biliary tract disease. In general, the starting age of examination for the general population is 50 years old, with annual examination of fecal occult blood and fiberoptic colonoscopy every 5 years; for relatives with family history of colorectal cancer, the starting age of examination is from 40 years old; for family members with hereditary colorectal cancer, the examination should start from the age of onset of the youngest colorectal cancer patient in the family minus 10 years. Change in bowel habits requires timely medical treatment. Change in bowel habits is often the earliest symptom of colorectal cancer. Experts suggest that when there is an increase in the number of bowel movements, blood in stool, diarrhea, feeling of urgency, or constipation, difficulty in defecation, or alternating between the two, one should be alert to colorectal cancer. Clinically, most of the patients who have these symptoms think they are hemorrhoids, enteritis, anal fissure, etc. and delay to seek medical treatment. At present, the main diagnostic methods of colorectal cancer include fecal occult blood test, barium enema, fiber colonoscopy and CT 3D imaging test. Among them, the most simple and effective method is fiberoptic colonoscopy, which can not only detect lesions but also biopsy to determine the nature of tumor and provide the most important basis for treatment plan design. However, more patients are afraid of colonoscopy because they think it is more painful. However, fiberoptic colonoscopy is currently the most effective way of examination. In fact, for most patients, the examination is not very uncomfortable, especially nowadays most hospitals have carried out painless colonoscopy, which makes the examination less uncomfortable. Experts suggest that the factors related to the development of colorectal cancer include diet, intestinal disease, genetic factors and exercise factors. The prevention of colorectal cancer should also start from these factors. Especially for dietary factors, “three highs and one low”, i.e. high-fat, high-protein, high-energy and low-fiber diet is a high incidence factor for colorectal cancer. Carotene, vitamin B2, vitamin C and vitamin E can reduce the relative risk of colorectal cancer, while vitamin D, calcium, onion and garlic foods have protective effects. It is recommended to change our dietary habits, eat less high-protein, high-fat, high-energy meat foods, less pickled and smoked meat foods, eat more vegetables and fruits rich in fiber and vitamins; pay attention to exercise and strengthen exercise to reduce the incidence of colorectal cancer.