To study the osteogenic potential of cultured bone marrow stromal cells (BMSCs) transfected with transforming growth factor β1 (TGF-β1) gene in vitro, cultured BMSCs were transfected with the complexes of pcDNA3-TGF-β1 and Lipofectamine Reagent in vitro. The cell proliferation was detected by MTT method and the morphological features of transfected BMSCs was observed. ALP stains and PNP method were used to measure ALP activity. In addition, the collagen type Ⅰ propeptides and mineralized matrixes were examined by immunohistochemical staining and tetracycline fluorescence labeling respectively. The morphological and biological characters of the transfected BMSCs were similar to those of osteoblasts and the cell proliferation was promoted. The cell layer displayed strong positive reaction for ALP stains and immunohistochemical staining. ALP activity and collagen type Ⅰ expression increased remarkably after transfection. Mineralized matrixes formed earlier and more in transfected BMSCs as compared with control group. It is concluded that transfecting with TGF-β1 gene could promote the osteogenic potential of cultured BMSCs.