Objective:To observe the relationship between myocardial apoptosis of diabetic mellitus and uncoupling protein 2 (UCP2). Methods:Diabetic animal models were induced by streptozotocinon on UCP2 knock-out mice(UCP2-/-) and C57BL/6 mice,rearing for 7 and 28 days each group. The expressions of myocardial apoptosis relative protein,caspase 3,were investigated using western blot. Hochest fluorescence staining detected morphological changes of myocardial cells in left venticle of diabetic mice. Results:Hochest staining results showed cells nuclear condensation,granular fluorescence and other typical features of apoptosis in DM-28-day group. Myocardium of diabetic mice exhibited significant concentration of chromatin at 7 days and aggravated at 28 days,with high fluorescence intensity. However,slight concentration of chromatin was detected on UCP2-/-+DM mice comparison of DM mice at 28 days. Image analysis showed that the expression of cleaved-caspase 3 protein levels decreased slightly in UCP-/-+DM-7-day group comparing with DM-7-day group(P > 0.05). The expression of cleaved-caspase 3 protein levels decreased significantly(P < 0.05)in UCP-/-+DM-28-day group comparing with DM-28-day group. Conclusion:UCP2 may be one of the most important factors which contribute to myocardial apoptosis of diabetic mellitus.