Object To observe the protective effect of total isoflavones of pueraria DC (TIP) on osteoporosis induced by estrogen deficient rat Methods 42 10 month old female SD rats were bilaterally ovariectomized and 10 animals were made sham operation (Sham) under anesthesia. After 7 d, the ovariectomized rats were divided into 4 groups: untreated control (OVX) group (n=12); 2 treated groups (n= 10 each), one with 100 mg/kg TIP ig and the other with 20 mg/kg TIP ig, and a niylestrol group (E 3) (n= 10) The total body bone mineral content (BMC), and bone mineral density (BMD) and bone biodynamics were detected at 4th and 7th month Results 1 Compared with OVX group, BMC and BMD in TIP 100 mg/kg group were increased by 14 6% and 12.1% at 4th month, by 6 8% and 14 2% at 7th month, while in TIP 20 mg/kg group by 7 8% and 6 9% at 4th month, by 8 6% and 14 9% at 7th month 2 The densities of femur in TIP 100 and 20 mg/kg groups were respectively increased by 3 8% and 3 4%, while those of tibia by 6 8% and 6 3% than that of OVX control group The Ca contents were increased by more than 15% in the TIP treated groups 3 The maximum load and structural strength of femur were increased by 16 1% and 19 4% in TIP 100 mg/kg group and 9 1% and 12 5% in TIP 20 mg/kg group than OVX control group These parameters in tibia were also improved 4 Uterine weights both in TIP 100 and 20 mg/kg groups were almost increased by one fold than OVX group Conclusion TIP can protect osteoporosis induced by ovariectomized rats and these effect may be attributable to its week estrogen like action