OBJECTIVE To investigate the effect of "Qiang Gu Kang Wei" prescription on bone metabolism in simulated weightless rats. METHODS Male SD rats were randomly divided into five groups: 1) free active control (FAC); 2) tail-suspended control (TS); 3) tail-suspended and treated with large dose of the prescription (TS + L) (30 g/kg); 4) tail-suspended and treated with middle dose of the prescription (TS + M) (20 g/kg); 5) tail suspended and treated with small dose of the prescription (TS + S) (10 g/kg). The experiment lasted 3 weeks. The effect of the prescription on bone biomechanical properties, bone density, bone mineral contents, and bone biochemical markers of bone metabolism were examined. RESULTS Bone biomechanical properties, bone density, total and bound bone gla protein (BGP) of serum all increased significantly in three groups treated with the prescription. CONCLUSIONS "Qiang Gu Kang Wei" prescription prevents bone loss, hence maintains bone density and bone biomechanical properties under simulated weightlessness.