Estrogen deficiency in menopausal women is the main cause of osteoporosis. Phytoestrogen could be a suitable candidate for treatment of post-menopausal osteoporosis. Recent studies showed that S. chinensis contains several lignans, which may be phytoestrogen. In this study, we investigated the ameliorative effects of S. chinensis on post-menopausal osteoporosis. 30% ethanol extract of S. chinensis (SC) was administered orally for 6 weeks after 7 weeks of ovariectomized-induced osteoporosis. Bone mineral density was significantly increased following increased serum osteocalcin levels by SC treatment. Histological analysis showed that SC reduced the increased growth plate of the epiphyseal plate in femur. In addition, pores within bone marrow cells filling the lateral and medial epicondyle were decreased. Serum estradiol concentration was significantly increased in the SC-treated group. The expressions of estrogen receptor-α and -β were increased in uterus and MCF-7 breast cancer cells by SC treatment. And two transcriptions of proto-oncogenes, c-fos and c-Jun, were suppressed by treatment of SC. From these data, we propose that S. chinensis attenuates post-menopausal osteoporosis with its phytoestrogenic effects. S. chinensis may have the potential to be used as an alternative for treatment of osteoporosis.