Fever is the most common symptom after surgery. In the first three days after gastric cancer surgery, most patients will have fever, but the body temperature usually does not exceed 38.5℃, which is due to the absorption of heat caused by surgical trauma and is generally normal. However, if high fever or prolonged fever occurs after gastric cancer surgery, it is abnormal and the cause needs to be found. The causes of fever after gastric cancer surgery can be divided into non-infectious and infectious, and non-infectious fever usually comes earlier than infectious fever. The main reasons for non-infectious fever are long operation time, more than two hours, extensive tissue damage, intraoperative blood transfusion, drug allergy, hepatotoxicity caused by anesthetic drugs, etc. The common causes of infectious fever are wound infection, abdominal infection, pulmonary insufficiency, pneumonia, urinary tract infection, deep vein placement infection, septic or non-septic phlebitis and fungal infection. If persistent fever after gastric cancer surgery, cancer fever should also be considered, which is generally related to the following factors: 1. rapid growth of malignant tumor, necrosis due to relative ischemia and hypoxia of tissues; 2. massive necrosis of tumor cells caused by treatment and release of tumor necrosis factor, resulting in fever of the body; 3. malignant tumor cells themselves can produce endogenous pyrogenic sources; 4. secretion of some active substances by tumor cells can cause fever; 5. In tumor treatment, radiotherapy, chemotherapy, application of interferon, interleukin-2, tumor necrosis factor, colony-stimulating factor, tumor vaccine and other agents can also cause fever.