Gastric cancer is a common malignant tumor of digestive system, and the reasons for patients with gastric cancer to vomit blood clinically include the following: 1. Gastric cancer is mostly ulcerative lesion, which is prone to bleeding on the surface of ulcer and is clinically manifested as vomiting blood. 2. When the lesion of gastric cancer metastasizes to the liver and causes serious damage to the liver function, resulting in the lack of coagulation factors, vomiting blood may also occur. 4. The metastasis of gastric cancer lesion to the spleen leads to hypersplenism and platelet decline, and in severe cases, spontaneous internal bleeding may also occur, which is also manifested as vomiting blood. 5. The advanced lesion of gastric cancer with coagulation dysfunction may also manifest as vomiting blood.