Abstract: The polymorphisms of myogenin gene in Mongolian sheep, Poll Dorset sheep, German meat Merino sheep and Suffolk sheep were analyzed by PCRSSCP. The results indicated that there were three genotypes(AA,AB and BB)detected by exonⅠ, and there weren’t polymorphism in exonⅡ. To amplify fragments by exonⅠ, AA and AB genotypes were detected in four sheep breeds. BB genotype was detected in Mongolian sheep, Poll Dorset sheep and Suffolk sheep.Frequency of AA genotype in Mongolian sheep was the highest , but frequency of AB genotype in other three breeds was high. Frequency of A allele was obviously higher than frequency of B allele in four sheep breeds. The polymorphic fragments amplified by exonⅠwere cloned and sequenced, and the sequencing results showed that there was one single nucleotide mutation :T→C at cDNA 305 of myogenin gene in sheep, and this mutation resulted in an amino acid change: cysteine→arginine.