The possible causes of fever in preoperative chemotherapy for bladder cancer include chemotherapeutic drug reaction, cancerous fever and so on. 1. Chemotherapeutic drug reaction: neutropenia is the most common hematological toxicity of chemotherapeutic drugs, and severe neutropenia on the one hand increases the risk of invasive infections. Infections in neutropenic patients usually progress rapidly, and since the patient is unable to generate a strong inflammatory response in such cases, they may manifest as nonspecific manifestations such as fever. 2. Carcinogenic fever: Due to the exuberant proliferation and destruction of tumor cells, in the process of tumor cell division and lysis, the endogenous thermogenic source generated by itself stimulates the thermoregulatory center, thus causing fever; on the other hand, due to the rapid growth of tumor tissues and ischemia and hypoxia, caused by its own tissue necrosis and treatment induced by the necrosis of tumor cells and the release of tumor necrosis factor, leading to the development of fever in the organism. If fever occurs after chemotherapy, it is recommended to go to the hospital in time.