Salvia miltiorrhiza Radix root extracts (SMR) was evaluated for inhibition of the progress of bone loss induced by ovariectomy (OVX) in rats. We measured body weight and bone histomorphometry in sham, OVX and SMR-administered OVX rats. From light microscopic analyses, porous or erosive appearances were observed on the surface of trabecular bone of tibia in OVX rats, whereas those of the same bone in sham rats and in SMR-administered rats were composed of fine particles. The trabecular bone area and trabecular thickness in OVX rats were decreased by $50\%$ from those in sham rats, and these decreases were completely inhibited by administration of SMR for 7 weeks. In this study, the mechanical strength in femur neck was significantly enhanced by the treatment of SMR for 7 weeks. In OVX rats, free $T_3$ was normal in all cases, whereas free $T_4$ was significantly increased. Although there was no difference between OVX and SMR-administered rat in $T_3$ levels, we have found significant difference between them in $T_4$ level. These results strongly suggest that SMR may be beneficial for preventing bone loss in OVX rats.