There are many causes of fever in one year old children such as infections, and non-infectious diseases. 1. Infection: one year old baby immune system is not fully developed, resistance is relatively low, when the upper respiratory tract is infected by pathogens such as mycoplasma, respiratory syncytial virus or streptococcus, etc., or improper diet leads to gastrointestinal infections, which will cause the baby thermoregulatory center disorders, which in turn increase the baby’s body temperature. 2. Non-infectious diseases: such as rheumatic fever, leukemia of the blood system, or oncological diseases, etc., can cause fever in babies. A year-old child fever may also have other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.