A case of glycogen accumulation disease type Ⅱ was reported.The patient was a 26-year-old male who presented with skeletal muscle atrophy and weakness of limbs and myocardial involvement in his youth.Laboratory and pathological data including creatine kinase,electromyography,nuclear magnetic resonance of lower limbs and muscle pathological biopsy suggested myositis changes.Enzymatic examination of peripheral blood lymphocyte filter paper showed deficiency of acid alpha glucosidase(GAA)activity.Genetic testing of GAA gene confirmed glycogen accumulation disease type Ⅱ.Genetic variation c-32-13T>G and c.1551+2T>G came from mother and father,respectively.Analyzing the characteristics of the patient could recognize and accumulate more data about glycogen accumulation disease type Ⅱ,in order to increase the understanding of the rare autosomal recessive genetic disease.