Fever is a clinical symptom that may occur in many diseases, and many cancer patients will also have fever. This is because during the transition period when cancer cells are multiplying vigorously, a large number of cancer cells will be necrotic and liquefied because the blood supply cannot meet the needs, and the necrotic and liquefied cells can release thermogenic substances, thus increasing the patient’s body temperature. How to distinguish cancer fever from fever caused by general germ infection? Fever in most diseases is accompanied by elevated white blood cells and accelerated blood sedimentation, while cancer fever sometimes has no abnormal laboratory findings even if the fever is high. Cancer fever lasts for a long time. The fever may be mild or severe, exceed 37.8℃ at least once a day and last for more than a few weeks, and continuous high fever may occur when accompanied by infection, and the fever may persist after the infection is eliminated. In cancer fever, the application of antibiotics and anti-allergy drugs has no significant effect, but the fever (especially high fever) can be reduced after the application of drugs such as methotrexate (naproxen). In many cases, cancer fever is often the first symptom before some other symptoms caused by cancer compression, liquefaction and enlargement appear. Because of the complexity of cancer changes, its symptoms may also have many variations. The above signs and symptoms of cancer fever only remind patients that if they have fever for no reason, they should not ignore the possibility of cancer and should go to the hospital for further consultation and treatment.