Abstract: The polymorphism of ESR gene in Landrace,Large White and Landrace譒arge White was detected by using PCR-RFLP.The correlation between the genotypes of ESR gene and reproductive traits was analyzed.The result indicated that ESR locus existed polymorphism in the 3 swine populations.The allele frequency was higher than 0.75,and the B allele frequency lower than 0.25.The reproductive traits (Total Number Alive,or TNB;Number Born Alive,or NBA;Birth Weight,or BW;Number Born Weaning,or NBW) of the first and later parities were affected by various genotype.They tended to be AAABBB.In addition,the reproductive traits (TNB,NBA,and BW) of all parities were also affected by various genotype with the same trend,i.e.,AAABBB.The TNB of the later parity and all parities was significantly different between AA and AB genotype (P0.05).