Colorectal cancer, including colon and rectal cancer, is a common malignant tumor in China. In recent years, due to the influence of diet and environmental factors, the incidence of colorectal cancer is increasing year by year, ranking 4th among all kinds of malignant tumors, and its 5-year survival rate is between 25-50%, which seriously affects people’s life. Therefore, how to take corresponding preventive and screening measures to reduce the incidence of colorectal cancer, improve the early diagnosis rate and prolong the 5-year survival rate is the task and goal of medical workers, and is also a great concern to the people. What are the methods of colorectal cancer screening? Commonly used methods are as follows: 1. Stool OB: the most commonly used, simple and easy, suitable for mass screening, can reduce the mortality rate of colorectal cancer by 15-33%, meat has influence, poor sensitivity and specificity, can be used as primary screening method. 2.Colonoscopy: it can observe the whole colon, biopsy and polyp treatment can be done, it is the gold standard for diagnosis of colorectal cancer, but the intestinal preparation is complicated, with certain pain and danger, high cost, it can be used as the re-screening method when other methods are positive. 3.Double contrast air-barium enema method: easy to miss diagnosis for small lesions, not treatable, poor sensitivity, not preferred for primary screening. 4, simulation colonoscopy (CT colon imaging), sensitivity up to 90-98%, relatively poor for less than 6mm, expensive to intestinal preparation, only as a re-screening method for patients who do not want colonoscopy. 5.Capsule colonoscopy: painless, non-invasive, requires intestinal preparation, expensive, whole colon picture is not fully satisfactory, cannot be biopsied and treated, can only be used as a supplement for reluctant colonoscopies. Who are vulnerable to bowel cancer? 1. Ulcerative colitis is not colitis in general, but colitis with recurrent episodes of pus and blood in the stool as the main symptom, and “sore mouth” like ulcers visible on colonoscopy. The chance of cancer in ulcerative colitis is 5 to 10 times higher than that of normal people, especially for those who developed the disease when they were underage, and the risk of cancer is greater for those who have been active, have extensive lesions, and have a disease duration of more than 5 years. 2. People with family history of colon cancer Studies show that the risk of colon cancer is 1.7 times higher than that of the general population when there is a colon cancer patient in the immediate family, and the risk is further increased when the age of onset of the disease in the immediate family is less than 55 years old or when there are two onset of the disease. Family history of colorectal adenomatosis is also associated with an increased risk of colorectal cancer. It is estimated that genetic factors play an important role in at least 20-30% of colon cancer patients. In addition, there is a family history of adenomatous colorectal cancer, mainly a mutation in an oncogene called APC, which causes many polyps to grow in the intestine. If the polyps are not treated at a certain time, almost all patients will become malignant before the age of 40. We know that the development of colon cancer is closely related to the environment, so people living in areas with high incidence of colon cancer should pay special attention to the occurrence of colon cancer. The environmental factors mainly include the lack of selenium in the soil and the influence of schistosomiasis, which is also a high incidence area of colon cancer in China. The detection rate of colorectal cancer is 12.3 times higher in areas heavily affected by schistosomiasis compared to areas without this disease.