Osteoporosis is characterized by the reduced density of mineralized bone matrix. The loss of bone has been attributed to an imbalance between bone formation and bone resorption. The silkmoth is one of the famous traditional tonic medicines. Silkworm pupa was evaluated for its antiosteoporotic activity in an ovariectomized rat model of osteoporosis. The rats were ovariectomized at 6weeks of age and divided into 7 groups. All the groups were fed without calcium diet. The OVX rats were treated with water and silkworm powder for 6 weeks. In OVX rats, the body weight, feeding and water intake quantity did not show a significant change, but the silkworm pupa powder immediately before the eclosion of Yeonrokjam was significantly increased the bone mineral density in the femoral bone. The silkworm pupa powder increased the bone with increasing calcium in serum. These results also showed its protective action through promotion of bone formation. The silkworm pupa powder has a definite antiosteoporotic effect; similar to estrogen, it is especially effective for the prevention of bone fracture induced by estrogen deficiency. The silkworm pupa powder is a promising anti-osteoporotic agent that can prevent bone fractures in osteoporotic patients. The silkworm pupa powder does not show serious side effects because natural herbal medicine origin.