There is no simplest way to determine whether a child has myocarditis. The judgment should be based on a comprehensive analysis of the typical history of antecedent infection, clinical manifestations, auxiliary examinations and other information. Common auxiliary examinations include electrocardiogram, myocardial injury marker test, echocardiogram, and non-specific inflammatory index test. Myocarditis can be suspected in children when they present with prodromal symptoms of infection such as fever, muscle aches and pains, often accompanied by palpitations and chest tightness 1-3 weeks before the onset of the disease. They should go to the hospital in time, under the guidance of the doctor, combined with auxiliary examination to clarify the diagnosis. The diagnosis of myocarditis can be considered when there are ST-T changes and various types of arrhythmias on the electrocardiogram; increased myocardial creatine kinase and troponin on the examination of markers of myocardial injury; enlarged cardiac chambers or abnormal ventricular wall activity on the echocardiogram and/or diminished left ventricular systolic or diastolic function on the nuclear cardiac function tests; and elevated erythrocyte sedimentation rate, C-reactive protein and other non-specific indicators of inflammation. The definitive diagnosis of myocarditis relies on endomyocardial biopsy, which, because it is invasive, is not usually performed routinely in patients with mild disease. When children are suspected of having myocarditis, they should go to a regular hospital in time and should not make blind judgments on their own, so as not to affect their condition.