Objective To investigate the effects of electrical stimulation on the differentiation of rat bone marrow mesenchymal stem cells (MSCs) to cardiomyocyte induced by 5-azacytidine in vitro.  Methods MSCs from Sprague-Dawley (SD) rats were cultured and passed repeatedly to P3. MSCs were treated with 5-azacytidine (10 μmol/L) and incubated for 24 h．The induced MSCs were divided to stimulated group and non-stimulated group

and every groups divided by incubated for 1

2，3 and 4 weeks were named as subgroup Ⅰ，Ⅱ

Ⅲ and Ⅳ respectively．MSCs of stimulated group were stimulated for 30 min every day by supra-threshold square biphasic pulses (2 ms duration

1.5 Hz

20 μA)

and the stimulation was initiated 1 d after inducing. Light and electronic microscope were used to identify the influences of characteristic morphological of MSCs in every subgroups，and immunocytochemistry was used to identify the expression of α-actin，cTnT

Cx43 in MSCs.  Results The growth of MSCs in stimulated group was better than that of non-stimulated group. MSCs of stimulated group exhibited differentiation into cardiomyocyte-like cell at 1 week after inducing

earlier than that of no-stimulated group (2 weeks). In stimulated subgroup Ⅰ

scattered myogenic structure was observed in the plasma of some cells under electronic microscope

and α-actin，cTnT expressed in some cells

but not that be observed in non-stimulated subgroup Ⅰ. In cells of stimulated subgroups Ⅱ to Ⅳ

the expression level of α-actin

cTnT

Cx43 of were all higher than that of non-stimulated subgroups respectively.  Conclusion Electrical stimulation (simulating the heart beating) could redound differentiation of rat bone marrow mesenchymal stem cells (MSCs) to cardiomyocyte induced by 5-azacytidine in vitro.