Abstract: To investigate the treatment role of bone marrow mesenchymal stem cell (MSCs) transp1antation on the model of acute myocardial infarction (AMI) and to observe the survived and transformationed MSCs in the infracted heart after 3 months. Methods: After established models of AMI, 20 miniswines were randomly divided into four groups (n=6), Model group: the animals only established models of AMI; Saline group: AMI immediately followed by saline injection take the place of MSCs implantation; MSCs group: AMI immediately followed by MSCs implantation. Three months after operation, detection the cardiac function in each group and observation the bone marrow-derived mesenchymal stem cell survival and transformation by Immunofluorescence microscopy. Result: Three months later, the ejection fraction (EF%) was significantly improvement in MSCs group [(50.2±5.3)% and (58.9±1.5), P<0.01] compared with saline group and the mass defect percentage(%) was decreased [(1.95±0.22)% and (-1.75±0.19)%, P<0.05] in MSCs group compared with saline group importantly, Immunofluorescence and histochemical results confirm that transplanted MSCs still alive after 3 months, and part of the experiment appears to have differentiated into cardiomyocytes and vascular endothelial cells. Conclusion: MSCs transplantation by directly injection into myocardial infarction can survive 3 months and differentiated into cardiomyocytes and vascular endothelial cells, on the other hand, the same kinds of the opposite sex MSC transplantation can improve cardiac function on the model of acute myocardial infarction .