Abstract: Objective To study the clinical characteristics and the effect of enzyme replacement therapy for late-onset glycogen storage disease type Ⅱ(GSDⅡ ). Methods The clinical, laboratory data and the result of genetic testing were retrospectively analyzed in a GSD Ⅱ child, the effect of enzyme replacement therapy was followed up and the relevant literature was reviewed. Results The patient had motor regression after 1 year old, the serum creatine kinase level is from 675 to 1286 U/L. The EMG test showed myopathic change, acid alpha-glucosidase activity is 12.0 nmol/(g·min), next generation sequencing of genetic muscle diseases panel found the GAA compound heterozygous mutations, both were tiny variations, and muscle biopsies showed the typical pathological features of GSD. The patient was given human recombinant of alpha glucoside enzyme 20 mg per kilogram of body weight, once every other week for 1 year. The weakness of the patient’s muscle strength had no obvious aggravation. Conclusions Early and adequate enzyme replacement therapy is the only possible treatment for GSDⅡ .