There are two main reasons for dark stools: First, dietary factors, eating dark-colored food, such as amaranth and animal offal, blood products, including pig blood, duck blood may appear dark stools, when stop eating this type of food stools can turn yellow. Second, intestinal or gastric bleeding, causing bleeding in the stomach for a variety of reasons, common peptic ulcer, including gastric ulcer, duodenal ulcer, acute gastric mucosal lesions, malignant tumors of the gastrointestinal tract can cause the performance of bleeding, bleeding is serious, in addition to the performance of black stool, there is vomiting blood. Therefore, the cause of black stool needs to be ruled out whether it is due to dietary factors, and if dietary factors are ruled out, gastroscopy and, if necessary, colonoscopy and small intestine microscopy are required for the appearance of bleeding.