The common causes of recurrent upper gastrointestinal bleeding include peptic ulcer, rupture of esophagogastric fundus varices, acute erosive hemorrhagic gastritis, gastric cancer, etc. Black stools are caused by the combination of iron in hemoglobin and hydrogen sulfide in the intestinal tract to produce ferrous sulfide. 1. The principle of black stool: generally related to the hemoglobin in the digestive tract contains iron, once encountered with hydrogen sulfide in the intestines, it will form black ferrous sulfide, causing black stool. 2. Causes of gastrointestinal bleeding: Causes of gastrointestinal bleeding include gastrointestinal ulcers, such as gastric ulcers and duodenal ulcers; acute erosive and hemorrhagic gastritis, tumors of stomach, duodenum, and esophagus, such as gastric and esophageal cancers; and other causes such as rupture of esophagogastric fundal varicose veins, and esophagogastric and pancreatic tears and bleeding, etc. In addition, if the condition is severe, it will cause black stools. In addition, if the condition of gastrointestinal bleeding is serious and harmful, it is suggested that patients need to actively treat it, and should not be negligent so as not to delay the condition.