Abstract: The prolactin receptor (PRLR) plays a key role in many reproductive pathways of animals. It is probable that the change of the structure of PRLR gene will lead to variation of PRLR function, and hence affect reproductive phenotype. In this experiment, the Nae I polymorphism of PRLR gene and its effect on reproductive traits in Minpig, Landrace and their F1 crossbreed sows was studied by sequencing and PCRRFLPs. A mutation of A to G (1 789) that resulted in a change of amino acid (S→G), i.e. Serine → Glycine was detected in cDNA sequence (+1 628+1 878) of PRLR gene. The frequencies of genotypes and alleles for Nae I polymorphism site were significantly different in three populations (P<0.01). The results of correlation analysis indicated that PRLR gene was closely associated with several reproductive traits examined. As regards Minpig, only two genotypes were detected, sows with AB genotype had significantly heavier litter weight at birth and higher piglets uniformity on day 21 than sows with AA genotype (P<0.05). For Landrace, sows with AA genotype have a greater litter weight on day 21 than sows with BB genotype (P<0.05). In the F1（L×M）crossbreed population, piglets uniformity on day 21 was significantly higher for sows with BB genotype than sows with AB and AA genotypes (P<0.05).