The polymorphism of prolactin receptor (PRLR) and retinol-binding protein 4 (RBP4) genes was detected by PCR-RFLP method, and the effects of PRLR and RBP4 genes on litter size traits in pig were analyzed by the least square analysis. Data of total number born (TNB) and number born alive (NBA) from 323 sows, including five Shandong local pig breeds and three foreign pig breeds, were collected. The results showed that the polymorphic sites of both PRLR and RBP4 genes were found in all populations tested. The genotype distribution, however, revealed great differences between Shandong local pig breeds and foreign pig breeds. The effects of genotypes on TNB and NBA were significant (P<0.05). The homozygote AA was the most prolific genotype. For PRLR gene, AA genotypic sows of Shandong local pig breeds and foreign pig breeds produced 1.03 TNB, 0.89 NBA, and 1.26 TNB, 1.11 NBA more than BB genotypic sows, respectively. For RBP4 gene, AA genotypic sows of Shandong local pig breeds and foreign pig breeds produced 0.59 TNB, 0.51 NBA and 0.72 TNB, 0.64 NBA more than BB genotypic sows, respectively.