A child’s normal body temperature is 35-37.5°C. A body temperature above this range is considered feverish. If the temperature exceeds 39℃, it is considered as high fever. For children with high fever for 5 days, we should actively look for the cause of the fever and take cooling measures while looking for the cause. We need to do some tests to find the cause: (1) routine blood tests: to see if there is an increase in the total number of white blood cells and neutrophils, if neutrophilia is very obvious, mostly due to serious bacterial infections, if mononuclear, lymphocytosis suggests that there is a viral infection, there is an infection, you need timely anti-infection treatment, after the infection is under control, the general temperature will drop. (2) urine routine: whether there is urine protein or white blood cells, to see whether there is a urinary tract infection. If there are symptoms such as frequent, urgent, painful urination, and urine protein, it indicates a bacterial infection, drink more water to flush out the bacteria. (3) Stool routine: see if there is infectious diarrhea, enteritis, etc.. If there is, prompt treatment, the body temperature will drop after the primary disease is controlled. (4) CRP and PCT: This is a sensitive indicator to detect bacterial infection, such as elevated, suggesting the possibility of bacterial infection. (5) Blood culture: This is an indicator to detect bacterial infection, if the culture is positive, it indicates infection. How to treat a baby with repeated fever of 39 degrees for 5 days? (1) Symptomatic treatment: For children with high fever for 5 days, it is necessary to choose antipyretic and analgesic drugs for treatment along with physical cooling to avoid damage to the organism caused by high temperature. And pay attention to keep the indoor air circulation, temperature and moderate appropriate, and use warm water to help the baby rub body. (2) Support treatment: timely hydration, let the baby drink more water, more sweating, more urination, reduce the body temperature. And to eat a light and easy to digest, or supplement some energy as appropriate. (3) Suggest hospital visit: further check blood routine, CRP and PCT, blood culture and other items to further find the cause and treatment.