Objective Genistein,as a phytoestrogen,is a type of soybean-derived isoflavone that possesses structural similarity to become estrogen. The purpose of this study was to elucidate whether the administration of genistein, extracted from a Chinese herbal medicine Huaijiao ( Sophora japonica-Leguminosae) ,is capable of preventing rapid bone loss occurring in rats after surgical ovariectomy and improving the symptom caused by this. Methods Sixty rats were randomly divided into six groups, including control (sham-operated), ovariectomized model ( OVX) , E2-treated (E2) group that were subcutaneously injected with E2 at a dosage of 1.5 mg/kg once a week,and genistein-treated (Gen) groups at the dosage of 4. 5 rag/kg,9. 0 mg/kg and 18 mg/kg respectively. The treatment was administrated 8 days later after the operation. Samples were taken from every group randomly at 12 weeks after the treatment. Parameters,such as body weight,serum biochemical criterion,bone mineral density(BMD) and biomechanics, were evaluated. Results The results indicated that genistein could restrain body weight, increase the levels of serum Ca,Mg,P,calcitonin(CT) and decrease the levels of bone gla protein ( BGP) and alkaline phosphatase (ALP) significantly. Compared with OVX group, genistein at the dosage of 4. 5 mg/kg and 9 mg/kg enhanced the BMD of femur, tibias and L2-4. Genistein could also meliorate biomechanical indexes of rats (P