The diagnosis of myocarditis is primarily a clinical diagnosis, and a definitive diagnosis requires an endomyocardial myocardial biopsy. Myocarditis is an inflammatory disease in which the myocardium is affected by various physicochemical factors, especially viral infections; at the same time, the clinical manifestations of myocarditis vary, and thus the main diagnosis of myocarditis is currently based on typical prodromal infection symptoms, such as upper respiratory tract infection symptoms such as fever, fatigue, muscle aches, or gastrointestinal symptoms such as nausea, vomiting, and diarrhea 1-3 weeks before the onset of the disease in patients; and includes palpitations, chest tightness, chest pain, and cardiac symptoms such as arrhythmia, heart murmur, heart failure, and shock when the myocardium is involved. Cardiac symptoms such as chest tightness and chest pain and signs such as arrhythmia, heart murmur, heart failure and shock; as well as electrocardiography, cardiac enzymology, echocardiography, cardiac MRI and other tests. However, if the diagnosis needs to be confirmed, it needs to be based on endomyocardial myocardial biopsy. Studies have confirmed that endomyocardial tissue biopsy has not only diagnostic value, but also prognostic assessment value. However, due to available equipment and clinical experience, endomyocardial tissue biopsy is not yet widely available in clinical practice. Especially for patients with mild disease, it is generally not routinely examined. The diagnosis of myocarditis is mainly based on the patient’s history of antecedent infection, corresponding clinical manifestations, physical signs and relevant examinations such as electrocardiogram, myocardial enzymes and echocardiography to make clinical diagnosis; the confirmation of diagnosis depends on myocardial cell biopsy.