Progressive muscular dystrophy (PMD) is an X-linked recessive primary muscular disease characterized by progressive muscular weakness. It causes gait disturbance and complications such as pneumonia, heart failure, and aspiration, so lead to death. Becker muscular dystrophy (BMD) is a milder type of PMD, of which incidence is 5 cases per 100,000 populations. It begins later and evolves more slowly than Duchenne muscular dystrophy (DMD). In PMD patients without heart failure symptom, there may be ECG abnormality or ventricular dilatation, impaired ventricular function which is consistent with dilated cardiomyopathy, especially in DMD. In BMD, heart failure is rare but ECG or echocardiographic abnormality is often found. With the advance of molecular genetics, mutations of the dystrophin gene is proved to be related to the pathogenesis of PMD and dilated cardiomyopathy. We confirmed the deletion of exon 43-51 in the dystrophin gene a case of BMD with asymptomatic dilated cardiomyopathy, diagnosed by echocardiography.