The glycogen synthase gene (GYS1), which encodes the rate-limiting enzyme for glycogen synthesis of skeletal muscle, is a promising candidate gene for traits related to skeletal muscle in pigs. In this study, a G/A single nucleotide polymorphism in GYS1 intron 7 detected as a FokI PCR-restriction fragment length polymorphism (PCR-RFLP) showed allele frequency differences among five Chinese indigenous pig breeds and three western commercial pig breeds. Linkage analysis assigned the gene GYS1 to marker interval SW1302-SW1473 on SSC6 in a three-generation Meishan X Large White reference family. The results of association analysis and interval mapping suggested that the FokI PCR-RFLP polymorphism might be linked with the quantitative trait loci affecting carcass traits detected on SSC6 in the F2 intercross pedigree. The reverse transcriptase-polymerase chain reaction revealed that the porcine GYS1 gene was expressed in spleen, lung, liver, kidney, small intestine, skeletal muscle, heart and stomach, with the highest expression in skeletal muscle.