Glycogen storage disease type III (GSD III), a rare autosomal recessive disease characterized by hepatomegaly, fasting hypoglycemia, growth retardation, progressive myopathy and cardiomyopathy, is caused by deficiency of the glycogen debranching enzyme (AGL). Direct sequencing of human AGL cDNA and genomic DNA has enabled analysis of the underlying genetic defects responsible for GSD III. To date, the frequent mutations in different areas and populations have been described in Italy, Japan, Faroe Islands and Mediterranean area, whereas little has been performed in Chinese population. Here we report a sequencing-based mutation analysis in 43 Chinese patients with GSD III from 41 families. We identified 51 different mutations, including 15 splice-site (29.4%), 11 small deletions (21.6%), 12 nonsense (23.5%), 7 missense (13.7%), 5 duplication (9.8%) and 1 complex deletion/insertion (2.0%), 31 of which are novel mutations. The most common mutation is c. 1735+ 1G> T (11.5%). The association of AGL missense and small in-frame deletion mutations with normal creatine kinase level was observed. Our study extends the spectrum of AGL mutations and suggests a genotype–phenotype correlation in GSD III.