Abstract: The work is to study the relationship between XbaI polymorphisms of the estrogen receptor(ER) gene and bone mineral density in Beijing Han women.Bone mineral density(BMD) was measured at lumbar spine,proximal femoral and arm by dual energy X-ray absorptionetry(DEXA) and ER gene was determined by polymerase Chain reaction-restriction fragment length polymorphism(PCR-RFLP) in 179 Beijing Han women.The frequency of the ER genotype of XX、Xx and xx was 0.302,0.464 and 0.234 in Beijing Han women.There was a signficant difference between premenopausal and postmenopausal women in the frequency of the XbaI genotype.The BMD of lumbar spine in postmenopausal women(0.836±0.18g/cm²)was significally lower than that in premenopausal women (1.038±0.14g/cm²)(P＜0.01) and the incidence of osteoporosis in postmenopausal women was 54.3%.The frequency of XbaI genotype of ER gene in Han women.There was apparently different from that in other races in and menopause effected on the frequency of XbaI genotype.The XbaI genotype of ER gene was nonassociated with BMD.and significantly associated with BMI.