The diagnosis of upper gastrointestinal bleeding is based on clinical manifestations, laboratory tests and imaging tests. 1. Clinical manifestations: Upper gastrointestinal bleeding usually presents with vomiting blood, black stool, blood in the stool, dizziness, fatigue, fever, etc. Hemorrhagic shock may occur when the bleeding is large. 2. Laboratory examination: if the vomit or fecal occult blood test is strongly positive, or the hemoglobin concentration, red blood cell count and hematocrit decrease, the diagnosis of upper gastrointestinal hemorrhage can be made, but respiratory bleeding must be excluded, and black stools caused by eating can be identified by medical history. 3. Imaging tests: electronic gastroscopy, selective arteriography, single photon emission computed tomography and capsule endoscopy can be used to diagnose upper gastrointestinal bleeding. If vomiting blood, black stool, or blood in the stool occurs, timely medical examination and symptomatic treatment should be sought to avoid delaying the condition.