Abstract: In this paper， genetic variation of the estrogen receptor （ESR） gene in Sujiang pig breeding generations were studied. The results showed that: AA， AB and BB genotype existed in 4-6 generations. Allele frequencies of A were 71.67%， 66.67%， 68.33% in three generations and those of B were 28.23%， 33.33%， 31.67%， respectively. In three generations， the frequency of A allele was significantly higher than that of B allele （P<0.05）. Total first birth number of AA， AB and BB allele was not significantly different from each other and total number born of the second to the fourth birth of AA and AB allele differed from each other while that of BB was higher than AA and AB. In future breeding， the BB genotype pigs should be selected to increase the total number born of Sujiang pig.

Key words: Sujiang pig, estrogen receptor, polymorphism