Objective To explore the optimal condition for the differentiation of rat bone marrow mesenchymal stem cells(MSCs) into cardiomyocyte-like cells EM>in vitro/EM> by using bone morphogenetic protein 2(BMP-2). Methods SD rat MSCs were isolated from rat bone marrow and cultured, then induced by BMP-2 for 72 hours. The cultured cells were observed by phase-contrast microscope. The immunohistochemical technique and laser scanning confocal microscope (LSCM) were used for detecting of the expression of desmin, α-sarcomeric actin and C-TnT. The induced cells were evaluated by a transmission electron microscope. GATA4 and α-MHC expression were detected by relative quantitative RT-PCR after 7, 21, 28 days of induction respectively. Results MSCs induced by BMP-2 stretched out pseudopodium.The direction of the cell arraying was similar gradually. MSCs induced by BMP-2 could be identified by the positive staining for desmin, α-sarcomeric actin and C-TnT. Desmin、α-sarcomeric actin-positive cells made up higher of all MSCs than C-TnT-positive cells. Desmin and α-sarcomeric actinpositive cells were about 37.28% and 63.94%. C-TnT-positive cells were about 34.66%. Transmission electron microscope showed that the induced cells had a cardiomyocyte-like ultrastructure: the nuclei were positioned in the center of the cell. A lot of mitochondria, rough endoplasmic reticulum and ribosome were founded in plasm, and paralleled myofilaments could be seen in cytoplasma or beside the adge of membrane. RT-PCR assessment showed that the differentiated cells began to express GATA4 from day 7 to day 28 of differentiation and began to express αMHC from day 21 to day 28 of differentiation. Conclusion MSCs ca