Purpose: Osteoporosis that occurred after menopause is one of the most common metabolic disease. and it is that bone mass significant decrease in comparison with normal people. Its symptoms are fracture, decrease of height, etc. The purpose of this study is to examine what are the effects of the Gamisoyosan on the aged ovariectomized rat model of postmenopausal osteoporosis. Methods: 24 female rats were ovariectomized and divided into normal group(normal), ovariectomized group(control), and treated with Gamisoyosan group(treated). During 8 weeks we dosed D.W to sham and control group, and dosed Gamisoyosan(105 mg/100 g) to experimental group. After 8 weeks we sacrificed rats and measured the body weight, albumin, P, Calcium, ALP, total cholesterol, triglyceride, AST, ALT, T4, estradiol, the femur weight, the tibia ash weight, trabecular bone area, trabecular thickness, osteoclast number. Results: The level of serum albumin, calcium, AST, ALT, estradiol in Gamisoyosan group showed significant increase in comparison with control group. The level of serum triglyceride in Gamisoyosan group showed significant decrease in comparison with control group. Trabecular bone area and osteoclast number in Gamisoyosan group showed significant increase in comparison with control group. Conclusions: Reviewing these experimental results, Gamisoyosan has shown to activate osteogenesis and prevent bone resorption, and it should show efficacy on prevention and improvement of osteoporosis after menopause.