Abstract: RBP4 gene was regarded as a candidate gene for reproduction traits of Beijing Black pig in this study, and the polymorphism was detected by PCRRFLP with restriction endomuclease MspⅠ. Three genotypes were found in Beijing Black pig, and the frequencies of allele A and B, polymorphism information content and heterozygosity were 0.529 6, 0.470 4, 0.374 1 and 0.498 2, respectively, which revealed a moderate polymorphism in this site. Statistical results of χ2 test indicated that this site fitted Hardy-Weinberg equilibrium (P>0.05). Meanwhile, the effect of polymorphism of RBP4 gene on TNB, NBA and WB were analyzed, the results indicated that the TNB, NBA and WB of multiparous sows with either genotype showed no significant difference (P>0.05). The sows of first parity with genotype BB had 1.04 and 0.31 litter size of TNB more than those with genotypes AA and AB, and the pigs of first parity with genotypes BB and AB had 1.47 and 1.35 litter size of NBA more than those with genotype AA, respectively. The results of genotype effective analysis indicated that allele B had the positive effect on TNB, NBA and WB, which might increase 0.282 0, 0.408 5 and 0.000 9, respectively, that was to say, allele B might be a favourable allele on TNB, NBA and WB.