Abstract: The aim of this study was to detect the polymorphism in exon 10 of porcine PRLR gene and study the effects of the polymorphic site on litter size traits in swine. A total of 221 pigs from Large White, Mashen, Shanxi Black and Shanxi White pig populations were used to detect the polymorphism of the exon 10 of PRLR gene by PCR-RFLP, and the simple univariate animal model was used to analyze the effects of the PRLR genotypes on total number born (TNB) and number born alive (NBA) at first parity. The results showed that there was a NaeⅠ polymorphic site within the exon 10 of PRLR gene. Two alleles of A and B, and two genotypes of AA and AB, were detected in examined populations. The A allele was the superior allele in any one of the four populations, with the frequencies ranging from 0.86 to 0.93. The PRLR genotype was significantly associated with TNB and NBA of first parity. Sows with AA genotype had 1.797 and 1.293 more TNB and NBA than those of sows with AB genotype (P<0.05). This implied that the reproduction performance of pig could be improved if the NaeⅠ polymorphic site detected in this study was applied as a genetic marker in pig breeding and production.