Cardiomyopathy is a heterogeneous group of myocardial diseases. Cardiomyopathy has been defined in the past as a disease of the heart muscle of unknown origin. Cardiomyopathy is equivalent to primary or idiopathic cardiomyopathy. With increased understanding of the etiology and pathogenesis of the disease, cardiomyopathy has been redefined as a disease of abnormal myocardial structure and function, without the coronary heart disease, hypertension, heart valve disease, or congenital heart disease that can cause myocardial abnormalities. Those with a clear etiology are defined as specific or secondary cardiomyopathies. Based on anatomical patterns and pathophysiology, cardiomyopathies are classified as hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), restrictive cardiomyopathy (RCM), arrhythmogenic right ventricular cardiomyopathy (ARVC), and non-segmented cardiomyopathies. The rapid development of molecular genetics in the last 20 years has led to the identification of a number of associated genetic mutations in different types of cardiomyopathies. The etiology of some cardiomyopathies has been clarified and the boundary between primary and secondary cardiomyopathies has changed. In recent years there has been a new classification of myocarditis that emphasizes the classification of cardiomyopathies from a genetic and genetic mutation perspective. The etiologic diagnosis of cardiomyopathy has received widespread attention. Pediatric cardiomyopathy differs from adult cardiomyopathy in terms of etiology, pathogenesis and clinical manifestations. Foreign epidemiological studies have found that the incidence of pediatric cardiomyopathy is 1.1~1.2/100,000, and the incidence in infants is 8~12 times higher than that in older children, and about 30~40 % of the cases have a clear cause after examination. Myocarditis accounts for 27% (only in dilated cardiomyopathy). These etiologies differ between hypertrophic and dilated cardiomyopathies. The low rate of access to etiologic diagnosis in children with cardiomyopathy may be related to the fact that the etiologies of cardiomyopathy are numerous and unfamiliar, that specific diagnostic tests are only available in a few hospitals (e.g., metabolic testing) or have not been translated into clinical practice (e.g., genetic testing for disease), and that there is a lack of clinical diagnostic procedures and norms. The diagnosis of the cause of cardiomyopathy is very important, and some cardiomyopathies have the hope of reversing to normal or obtaining significant improvement after treatment with a clear cause. There is still a big gap in the diagnosis of the cause of pediatric cardiomyopathy in China, which requires attention and active research and communication.