Fever is a common symptom in pediatrics. Whether or not a toddler with a fever of 39.5℃ needs to go to the emergency room is related to the baby’s mental condition and the recurrence of body temperature, which needs to be analyzed specifically. Fever can be seen in a variety of diseases, such as respiratory tract infections, urinary tract infections or intracranial infections and other diseases, is a common symptom of pediatrics, fever is recommended to clarify the causes of fever, and the use of appropriate treatment and antipyretic methods. Whether or not a toddler with a fever of 39.5°C needs to go to the emergency room depends on whether or not the cause of the fever has been identified, the baby’s mental status, the degree to which the temperature has dropped with the use of antipyretic medications (e.g., acetaminophen or ibuprofen), and the presence of other abnormal symptoms. If the cause of fever has not been determined, the baby’s temperature does not drop satisfactorily with the use of antipyretics, or the baby’s mental response is poor, or the baby has convulsions, the baby needs to go to the emergency room immediately to avoid delaying treatment. If the cause of fever has been clearly identified (e.g. acute upper respiratory tract infection), reasonable use of antipyretics can be reduced to normal temperature, the mental response of the baby is still good can be deferred to go to the emergency room, close observation at home, and reasonable to the cause of the symptomatic treatment. The above medication should be used under the guidance of a doctor, avoid self-medication.