1.Change of stool habit and nature: In the early stage of rectal cancer, there are only small mucosal nodules and there are no conscious symptoms, but gradually the number of bowel movements increases, the stool is mucus stool, pus and blood stool, anal cramps, constipation, abdominal pain, diarrhea, etc. The shape of stool is flat and strip-shaped, and as the disease worsens, there are difficulties in defecation, incontinence, blood stool, foul odor, severe local pain, and different degrees of intestinal obstruction. The symptoms of the disease. 2, the general condition of the change: weight loss, and even wasting, anemia. 3. Rectal diagnosis: most of the lumps can be palpated when examining rectal cancer, the lumps protrude into the intestinal cavity, and the intestinal cavity becomes narrow. 4.Abnormal abdominal examination: in the middle and late stage, the tumor can be found in the abdominal wall, accompanied by enlarged liver and spleen and ascites. 5.Fecal occult blood test: For patients suspected of colorectal cancer, fecal occult blood test should be performed repeatedly, which is also meaningful for early detection of colon cancer and rectal cancer. 6.X-ray barium enema imaging: it has diagnostic value for early detection of rectal cancer and sigmoid colon cancer. 7.Proctoscopy, sigmoidoscopy or fiberoptic colonoscopy: it can directly determine the location and scope of lesions, and can also take biopsies of suspicious lesions for pathological examination, which is very important for the diagnosis of colon cancer. Besides, if intestinal polyps are found, they should be removed in time, which is also meaningful for the prevention of cancer.