A child’s heartbeat is particularly fast when he has a fever, considering that it is a common reaction to fever, but it may also be the presence of viral myocarditis and other diseases. 1. The common reaction to fever, the child fever due to the body temperature gradually rise, the body consumes energy and oxygen gradually increased, may lead to the metabolic rate accelerated, so there will be a particularly fast heartbeat symptoms. 2. Viral myocarditis, part of the child fever is caused by viral myocarditis, due to the virus invades the myocardium part may lead to myocardial blood supply is insufficient, the heart function is reduced, so there may be a particularly fast heartbeat symptoms. Children’s fever heartbeat especially fast, there may also be 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.