Previous studies suggested that the myostatin-1(MSTN-1) gene played as an important role in the growth and development of grass carp (Ctenopharyngodon idella). In order to determine whether the polymorphism of grass carp MSTN-1 gene was associated with growth traits and muscle compositions, 192 individuals from Yangtze River were used in this study. Three polymorphic loci were found in the 3824 bp MSTN-1 gene: C1799T, C1842T and TGAAGCGCTGGTTCT /2585-, which were named Locus 1 (wild-type EE/mutant EF), Locus 2 (wild-type HH/mutant HI) and Locus 3 (wild-type BB/deletion type BD), respectively. A general linear model was used to analyse the correlation between those three single nucleotide polymorphisms (SNPs) and grass carp traits. The results showed that two SNPs have a significant influence on grass carp growth traits. Whereas, none of those SNPs have a significant effect on grass carp muscle compositions. Multiple comparisons found that the body length and body weight of individuals with HI genotype were significantly higher than that of wide-type individuals, conversely, mutant individuals with BD genotype were significantly lower than wide-type individuals at body length and body weight in haplotype analysis; the groups with HI or BD genotype also had the similar results in fold type combinations analysis, while the body length of groups with BD genotype were not significantly lower than other groups. Results indicate that HI is a beneficial mutation on growth traits, while BD is a detrimental mutation on grass growth traits. Preliminary study indicated the MSTN-1 gene could be a candidate modifier gene in Molecular Marker-assisted Selection (MAS) of grass carp.