Objective：To investigate the effect of simvastain on the expression of BMP-2 and Smad1／5 in rats with ovariectomy-induced osteoporosis，and thus elucidate the mechanism of BMP-2 and Smad1／5 in nosogeny of osteoporosis and the regulating effect of simvastain. Methods：54 female SD rats were divided into three groups randomly：the experimental group，control group and model group .8 weeks after ovariectomy and sham-operation, simvastatin of 5 mg／（kg·d） were administered orally to the experimental group, and normal saline to the other two groups. Half of the rats were killed separately 4 weeks and 12 weeks after administration. Expression of BMP-2 and Smadl／5 in metaphysis of tibia was detected by immunochistochemistry. Results：① 4 weeks after administration，expression of BMP-2 was higher in experimental group and control group than that in model group（P < 0.05 or P < 0.01）; ②12 weeks after administration，expression of BMP-2 and Smadl／5 was higher in experimental group and control group than that in model group（P < 0.05 or P < 0.01）; ③Number of Smad1／5 positive cells and Smad1／5 gradation in experimental group was higher at 12 weeks after administration than 4 weeks（P < 0.01）. Conclusion：Hypo-expression of BMP-2 and Smadl／5 may be an important mechanism in nosogeny of primary osteoporosis. Simvastain can up-regulate BMP-2 expression in bone. Long-time administration of Simvastain can up-regulate Smadl／5 expression that may be an important mechanism of prevention and cure of osteoporosis.