Persistent low fever without other symptoms has various causes, and the common ones are primary low fever, infectious fever and non-infectious fever. 1. Primary hypothermia: it is also called somatic hypothermia, which has no organic lesion and may be related to the disturbance of the thermoregulatory center or autonomic dysfunction. 2. Infectious fever: bacterial, fungal, viral, parasitic infections may cause low fever, such as tuberculosis, brucellosis, AIDS and so on. 3. Non-infectious fever: rheumatic diseases such as rheumatism, rheumatoid rheumatism, ankylosing spondylitis; immune system diseases such as systemic lupus erythematosus, leukemia, adult still’s disease; hematological disorders such as leukemia; neoplasms; deep vein thrombosis fever; antibiotics, anesthetics caused by drug fever. Persistent low fever without other symptoms, there may be other reasons, it is recommended to consult a doctor to clarify the cause of the disease, timely treatment, to avoid delaying the condition.