Bowel cancer is a malignant tumor with a very high incidence rate, and the incidence rate of colorectal cancer in China has reached 13% in 2015, and the figure is still on the rise today. To prevent colorectal cancer, besides maintaining a good diet and lifestyle, choosing the right screening method is also of paramount importance. When many people hear of colon cancer, they think of colonoscopy. Colonoscopy is indeed a very effective screening method, but it is not the only method. Experts remind that there are 4 weapons to screen colon cancer. To detect bowel cancer as early as possible, you can firstly judge from early symptoms. 1.Change of bowel habit: such as diarrhea, constipation, anal swelling, feeling of incomplete bowel movement. 2.Blood in stool: this is a more obvious early symptom, but it is easily confused with hemorrhoids, so we must learn to distinguish. If the blood in stool is caused by colorectal cancer, it is mostly dark red, bright red or tar-like, and it is pus and blood in stool. 3. Deformed stool: normal stool is cylindrical, but if there is a tumor in the intestine, the stool will become thin and flat, and sometimes there are blood marks attached to the deformed stool. Precancerous lesions: Precancerous lesions of colorectal cancer are clearer, mainly familial adenomatous polyposis, adenoma and ulcerative colitis, which should be treated as soon as possible to reduce the chance of occurrence of colorectal cancer.