To compare the effect of different genes on litter size, we used PCR-RFLP to test the genotypic frequencies of 5 genes related to litter size, i. e. ESR, FSHbeta, PRL, PRLR and NCOA1 and analyzed the effect of various genotypes on total number born (TNB) and number born alive (NBA) within the same populations of Large White (n=158) and Landrace (n=224) pigs. Results showed that the PRLR and NCOA1 loci exerted the greatest impact on litter size: the average TNB from genotype AA was 2.28-3.33 more than that from BB (P<0.01) and the average NBA from AA was 1.57-3.30 more than that from BB (P<0.01). The ESR and FSHbeta loci had a moderate effect on litter size. The average TNB of BB being 0.55-1.18 more than AA (P<0.05) excluding the Landrace, and the average NBA of BB was 0.37-1.20 more than AA (P<0.05). The PRL locus had no significant effect on litter size.