The common causes of fever eight days after surgery are incision infection, pneumonia, cold and so on. 1. Incision infection: after surgery, if you do not do a good job of wound cleaning and hygiene care, resulting in infection of the incision, then the patient will be prone to fever, and the incision site may also show redness, swelling, pus and other symptoms. 2. Accumulative pneumonia: mostly seen in bedridden old people after surgery, easy to inhale when eating, and coughing sputum is more difficult, which leads to the accumulation of sputum and other secretions in the lungs, causing accumulative pneumonia, fever, coughing, coughing up sputum and other symptoms. 3. Cold and flu: After the surgery, many patients’ immunity will be somewhat reduced, which will easily cause certain viral or bacterial infections, thus resulting in cold and flu, dizziness, fatigue, fever and other symptoms. In conclusion, there are many reasons for fever eight days after surgery, it is recommended to reflect the situation to the doctor in a timely manner, so as to avoid more serious consequences of untimely treatment.