The baby fever after three days and then again, may be not fully recovered, medication is not right, infection of new pathogens and other reasons. 1. not fully recovered: the baby fever after taking antipyretic drugs due to the role of drugs, fever subsides, but the disease is not completely cured, prematurely stop the drug, may appear baby fever three days after the fever again. 2. medication is not appropriate: such as the child is a bacterial infection, but parents give the application of antiviral drugs for treatment, although the symptoms of fever eliminated, but the causative factors are still present, once the drug is discontinued, there will be a baby fever three days after the fever and fever. 3. Infection of new pathogens: in the baby viral infection just when the resistance and immunity is weak, if eat too much, again cold or go out to play more fatigue, may make the baby infected with new pathogens, resulting in the baby fever three days after fever again. The baby fever after three days of fever, there may be other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.