Diagnosis of the etiology of upper gastrointestinal bleeding mainly includes peptic ulcer, acute erosive hemorrhagic gastritis, gastric cancer, and rupture of esophagogastric fundal varices. 1. Peptic ulcer: peptic ulcer refers to ulcers caused by gastrointestinal mucosa being digested by gastric acid or pepsin itself. It mainly refers to the ulcers that occur in the stomach and duodenum, namely gastric ulcer and duodenal ulcer. Continuous aggravation of the condition leads to the ulcers being active for a long period of time, which can easily cause bleeding of the ulcers and lead to upper gastrointestinal bleeding. 2. Acute erosive and hemorrhagic gastritis: taking non-steroidal anti-inflammatory drugs will cause the barrier of gastric mucosa to be damaged, so that pepsin will enter into gastric mucosa in reverse direction and lead to acute erosion and bleeding of gastric mucosa, causing upper gastrointestinal bleeding. 3. Gastric cancer: when suffering from gastric cancer, the cancer cells invade the gastric mucosa and lead to mucosal breakage, or invade the gastric fundus artery, which will lead to upper gastrointestinal bleeding. 4. Rupture of varices of esophagogastric fundus vein: patients with history of liver cirrhosis and continuous aggravation of the condition leading to the stage of decompensation of liver function will have varices of esophagogastric fundus vein, which will easily induce upper gastrointestinal bleeding once the varices are ruptured. It is recommended that patients with upper gastrointestinal bleeding should go to the hospital in time to have the cause clarified under the guidance of professional physicians and be treated actively.