First, consider anal fissure, anal fissure is a longitudinal ulcer between the dentate line and the anal verge, will stimulate the sphincter muscle caused by the pain of defecation, but also more accompanied by blood in the stool, and the pain is more characteristic, the beginning of defecation pain, defecation in the middle of the pain to reduce the pain, defecation and the pain behind the back of their own relief, it is recommended that the internal medicine conservative treatment, such as warm water sitz baths, use some hemorrhoidal suppositories, attention! Avoid spicy and stimulating diet, avoid dry stool, if more than three months has not been relieved, can consider surgery, do anal fissure resection or part of the sphincter off surgery. Second, consider hemorrhoids, especially some external hemorrhoids internal bleeding to form thrombosed external hemorrhoids, defecation will also be painful. Third, perianal infection or perianal abscess, because of inflammation stimulation, in defecation will be particularly painful, do anoscopy basically can be diagnosed, hemorrhoids are generally symptomatic treatment and anal fissure is almost the same, the perianal infection should be active antibiotic anti-infection treatment, and even surgical treatment.