Abstract: AIM: To explore the preventive effect of stanozolol, a synthetic hormone, on osteoporosis, a prednisone induced osteoporosis model was established. METHODS: Twenty four male 3 month Sprague Dawley(SD) rats were divided into 3 groups randomly. Group A rats were controls; Group B rats were given prednisone acetate 4.5 mg·kg^-1 orally as osteoporosis model group; Group C rats were given stanozolol 0.5mg·kg^-1 orally besides prednisone acetate. The three groups of rats were treated twice a week for 90 d. The histomorphological parameters of bone slides of the proximal tibia were calculated with image pattern analyser and the blood biochemical indexes were measured. RESULTS: Compared with group A, the area and number of trabecula decreased but the intertrabeculer space increased in group B. The bone formation decreased and the osteoporosis model was set up successfully. However, in group C, stanozolol inhibited markedly the rate of bone absorption and showed effect of accelerating the formation of new bone. The bone mass increased significantly so that osteoporosis was prevented effectively. No toxic action was found both in prednisone and in stanozolol treated rats through testing the biochemical indexes of liver and kidney. CONCLUSION: Stanozolol has preventive effect on prednisone induced osteoporosis.