Black stool also refers to tarry stool, only refers to the black, the surface with mucus and the color of the shiny feces, while black stool is also mostly seen in the upper gastrointestinal tract, small intestinal bleeding or the use of special foods, the causes of black stool: 1, acute and chronic gastritis, peptic ulcer, etc. 2, taking special medicines or foods, such as animal offal, animal blood, bismuth, iron and so on. 3, esophageal cancer, gastric cancer, duodenal and other cancers, which may be accompanied by lethargy, weight loss, Weight loss, fatigue and other symptoms.4. Diseases such as esophageal varices, cirrhosis of the liver, etc.5. Abdominal trauma, which can be further combined with laboratory tests such as blood routine, liver function, coagulation function. Imaging tests such as abdominal CT, abdominal ultrasound. Other tests such as gastroscopy, enteroscopy, etc. to clarify the cause of the disease, to identify the black stool caused by taking special food, and to clarify the direction of treatment according to the test results.