The rapid heartbeat of children with fever may be related to the increase in oxygen consumption of the body, compensatory increase in heartbeat, sympathetic nerve excitation and other reasons. 1. Increased body oxygen consumption: In the case of fever, the body’s basal metabolic rate will increase, thus increasing the body’s oxygen consumption. In order to meet the body’s needs, the heart rate increases. 2. Compensatory increase in heart rate: If there is a severe infection causing fever, it will lead to a decrease in the effective circulating blood volume, which will lead to a compensatory increase in the heart rate. 3. Sympathetic nerve excitation: after a fever, the body will make a stress response, causing sympathetic nerve excitation, so it will also lead to a faster heart rate. Children with fever heartbeat, there may be other reasons, such as myocarditis, etc., it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.