Abstract: Objective and MethodThe polymorphism of bone morphogenetic protein receptor type IB gene (BMPR-IB gene) of 204 sheep of three breeds or strains ,which included Small Tail Han sheep,F_1 generation from German Merino(♂)×Small Tail Han sheep(♀) cross generation （DF1）, German Merino ,was analyzed by PCR-sscp. The relationship between genotype and litter size was also identified.Result and ConclusionThe results showed that the frequency of B allele in Small-Tail Han sheep, German Merino and DF1 was 0.660,0.532 and 0.600，there was no significant difference of distribution of gene frequency and genotype frequency in 3 groups.The litter size of BB,B+ and ++ was 2.86,2.27 and 2.08，BB were both significantly higher than B+ and ++ (P＜0.05),and B+ were significantly higher than ++ type.