Objective: The aim of this study is to investigate the effect of osteogenesis about Static magnetic field acting on rat bone marrow mesenchymal stem cells during osteogenic differentiation in vitro.Get a preliminary understanding of the role of SMF into the bone.Methods: The experimental BMMSCs were divided into 2 groups, which were experiment group and control group, and both of them were induced by differentiate medium.Experiment group was exposed to SMF at 200 mT 24h/day during osteogenesis.Contrarily, control group was not exposed to SMF during osteogenesis.We use MTT and Mineralization Assay method to detect the effect of osteogenesis.We collected the cells and then used western blotting method to analysis the protein expression of BMP-2 and COL I.