Blood in the stool is an abnormal manifestation of blood discharge through the anus, and is one of the common symptoms of anorectal diseases. It is often manifested as acute haemorrhage, chronic small amount of bleeding and intermittent bleeding, the color can be bright red, dark red, black stool, etc.. The symptoms of blood in stool are different for different diseases: 1. Internal hemorrhoids show bright red stool, painless, not mixed with stool, dripping down, or even spraying; 2. Patients with rectal cancer have frequent changes in stool habits, such as frequent bowel movements and dark red fecal blood mixed with mucus, which have not attracted clinical attention. In order to clarify the final diagnosis of blood in stool, it is necessary to take a detailed medical history and combine it with other symptoms and signs for comprehensive diagnosis and treatment.