Two polymorphic sites in the first exon 1 of MSTN gene in 180 Wenling grass-chicken including 3 lines were studied by PCR-RFLP method,and its genetic effects on carcass traits were researched. The results showed that 2 genotypes (MN and NN) in G(2100)A locus were identified by Bsh1236Ⅰand 3 genotypes (AA, AB and BB) in G(2109)A locus were identified by MspⅠ, and 5 genotypes were emerged while com-analyzing 2 loci. The c2 test indicated genotype frequencies had no significant deviation (P > 0.05) among lines. The analysis of variance showed that the different genotypes had significant deviation (P < 0.01 or P < 0.05) in carcass percent. The multiple comparisons were made. The abdominal fat weight and carcass percent of heterozygosis MN were significantly higher (P<0.05) than that of mutant NN,and the breast muscle weight and breast muscle percent of heterozygosis AB were significantly higher (P < 0.01 or P < 0.05) than that of AA indi-viduals. In addition,the abdominal fat weight and abdominal fat percent of AA individuals were significantly higher (P < 0.01) than that of mutant BB individuals,but BB individuals were significantly lower (P < 0.05) than AA and AB individuals in leg muscle weight trait. The abdominal fat weight,abdominal fat percent and breast muscle percent of genotype NA/MA individuals were significantly higher or lower (P < 0.01) than those in other genotype individuals while com-analyzing 2 loci.