Objective To summarize the clinical features of non-classic infantile glycogen storage disease type Ⅱ for early diagnosis. Methods The clinical data including the clinical manifestations and investigation of the 3 non-classic infantile glycogen storage disease type Ⅱ were retrospectively reviewed from Jun. to Jul. 2011. All the 3 cases were diagnosed by measuring acid α-glucosidase(GAA) activity in blood sample. Results All the 3 patients presented development delay, limb muscle weakness without hepatomegaly. Two cases of them presented weakness of respiratory muscle. The serum creatine kinase, aspartate aminotransferase and alanine aminotransferase were high in all the 3 patients. Electromyography studies indicated that one of the patients with susceptible myopathy, one patient with neurogenic damage and one patient with mixed damage of the neuromascular. Echographic evidence of hypertrophic cardiomyopathy was detected in 2 patients. GAA activity of the 3 patients in blood sample had diagnostic value. Conclusions Non-classic infantile glycogen storage disease type Ⅱis easy to be missed due to its non-significant clinical manifestations. The results suggested that GAA activity in blood sample should be screened for the patients with motor development delay, decreased muscle weakness/exercise tolerance and increased of serum creatine kinase. Key words: Infantile glycogen storage disease type Ⅱ; Acid alpha-glucosidase; Creatine kinase