A 3-year-old child with a persistent high fever needs to do the following: 1. reduce fever, antipyretic measures include medication and physical cooling, common antipyretic drugs include oral ibuprofen and acetaminophen, oral antipyretic according to the child’s weight. 2. physical cooling can be carried out, common physical cooling are ice packs on the head, warm water baths, unpacking the child’s clothing for heat dissipation. The most common causes of fever in 3-year-olds are respiratory infections, including tonsillitis, laryngitis, and pneumonia, which require a hospital visit to determine the cause of the fever.