Gastrointestinal bleeding is associated with diseases of the digestive tract itself, mechanical injury, and systemic bleeding disorders. 1. Digestive tract own disease: peptic ulcer is a more common cause of upper gastrointestinal bleeding, which may be related to long-term use of non-steroidal anti-inflammatory drugs, Helicobacter pylori infection and so on. In patients with severe liver disease, there will be esophageal varices, which will lead to gastrointestinal bleeding. Gastric cancer and colon cancer can lead to GI bleeding. Hemorrhoids and anal fissure are common causes of lower gastrointestinal bleeding. 2. Mechanical injury: foreign body injury in digestive tract and rupture of liver and spleen caused by trauma can cause gastrointestinal bleeding. 3. Systemic bleeding disorders: allergic purpura, hemophilia, primary thrombocytopenic purpura and other systemic bleeding disorders can also cause gastrointestinal bleeding. When gastrointestinal bleeding occurs, it is recommended to go to the hospital in time to find out the cause and get timely treatment.