Abstract: AIM: To explore the effect of organic internal environment on directional differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs) during transplantation of cardiac muscle cells. METHODS: BM-MSCs were identified by flow cytometry and immunocytochemical staining. hMSCs were then injected by vena caudalis into athymic mouse with myocardial damage done by isoprenaline as cardiac cellular transplant. Three weeks after cellular transplant, the damaged heart was immunohistochemically stained. RESULTS: hBM-MSCs highly expressed CD44, CD105 and vimentin but not CD31, CD34, CD45, troponin I and desmin. The cells differentiated from hBM-MSCs in the heart of athymic mouse with myocardial infarction positively expressed troponin I, desmin and vimentin. CONCLUSION: hBM-MSCs can be cultured and proliferated in vitro. hBM-MSCs are signaled and recruited in myocardial damage where they undergo differentiation into cardiomyocytes and may participate in the healing of myocardial damage.