The duration of fever in babies needs to be based on the cause and severity of the fever, if it is caused by upper respiratory tract infection, usually 3~5 days can recover. Clinically there is no specific data to indicate the specific duration of the baby’s fever, the duration of the baby’s fever needs to be judged according to the child’s condition. If the bacteria and viruses and other pathogens infect the upper respiratory tract infection, the main symptoms of the child for cough, fever, runny nose and so on. If the fever caused by the upper respiratory tract infection is self-limiting, usually fever can be recovered in 3 to 5 days. In addition, babies with pneumonia will also have symptoms such as coughing, coughing up sputum and fever. Pneumonia caused by fever is generally more serious, there will be a persistent high fever phenomenon, the fever is longer, the fever lasts for 5 to 7 days. There are also some special diseases caused by fever, such as leukemia, tuberculosis, etc., which usually require active treatment of the original disease to relieve the symptoms of fever. When a baby has a fever and cannot accurately determine the duration of the fever, parents should take their children to the doctor in time, and the doctor will determine the exact duration of the fever according to the cause of the fever.