Aim To observe the effect of IMD on ischemia-reperfusion induced myocardial apoptosis in diabetic rats and to explore its possible mechanism. Methods A total of 74 healthy male SD rats were randomly divided into diabetic group (50 rats) and non-diabetic group (24 rats) after one week of adaptive feeding. The non-diabetic group was given intraperitoneal injection of citric acid buffer, and diabetic group was established by intraperitoneal injection of streptozotocin. The myocardial ischemia-reperfusion injury model was prepared by blocking the left anterior descending branch of rat coronary artery. In the non-diabetic group, 24 rats were randomly divided into control group and ischemia-reperfusion (NIR) group. In the diabetic group, 36 rats of diabetes models were successfully established, and randomly divided into diabetic control group, diabetic ischemia-reperfusion (DIR) group and IMD group, 12 rats in each group. The morphological changes of myocardial cells were observed by light microscope, the ultrastructure of heart was observed by electron microscope, the apoptosis rate of cardiomyocytes was detected by TUNEL, the protein expression of Caspase-3, Bcl-2 and Bax was detected by Western blot. Results Ischemia-reperfusion could be observed under light microscope. The changes of myocardial cell injury in DIR group were more severe than those in the corresponding control group. The degree of degeneration and necrosis in IMD group was significantly lower than that in DIR group. Under electron microscope, the myocardial cell injury in NIR group and DIR group was more severe than that in the corresponding control group. The ultrastructure of myocardial tissue, especially mitochondrial damage in IMD group was significantly reduced compared with that in DIR group. The apoptosis rate in NIR group and DIR group was significantly higher than that in the corresponding control group (P＜0.05), and the apoptosis rate in IMD group was significantly lower than that in NIR group (P＜0.05). The protein expression of Caspase-3, Bax and Bcl-2 in NIR group and DIR group was statistically and significantly different from that in the corresponding control group (P＜0.05), the protein expression of Caspase-3, Bax and Bcl-2 in IMD group was statistically and significantly different from that in DIR group (P＜0.05). Conclusion IMD has protective effect on myocardial ischemia-reperfusion injury in diabetic rats, and its protective effect may be related to the reduction of cardiomyocyte apoptosis by IMD.