The PCR-SSCP polymorphism of myostation (MSTN) gene sequence of intron 2 and its correlation with growth traits were investigated in 277 individuals from one cultivated yak breeds (Datong yak) and two native breeds（Gannan and Tianzhu White yak).The results showed that there were two alleles and three genotypes in the locus of MSTN gene intron 2.They were at Hardy-Weinberg equilibrium state in this locus while Datong yak obviously was unequilibrium.The least square analysis showed that the different genotype of MSTN intron 2 had a significant effect on partial traits of growth including heart girth,body weight,index of chest circumference,index of body slanting length,beef performance index(P＜0.05).However the genotype did not affect body height,cannon circumference,body slanting length,index of cannon circumference significantly(P＞0.05).In conclusion,the mutation of MSTN intron 2 could be used as the molecular genetic marker for yak breeding.