Abstract: Objective: To observe the protective effect of diazoxide preconditioning on rat myocardial ischemia-reperfusion injury in vivo and observe the effect of diazoxide preconditioning on connexin 43 (Cx43) .Methods: Forty-five male SD rats were randomly divided into five groups: sham group， IRI group， IPC group，DPC group and 5-HD group，9 rats in each group.Myocardial ischemiareperfusion injury model was established by ligation of left anterior descending coronary artery for 30 minutes， followed by 120 minutes of reperfusion.The left ventricular systolic pressure， left ventricular diastolic pressure and other heart function were measured by Medlab biological signal collecting and processing system.After reperfusion，myocardial enzymes in plasma were tested; and then the expressions of TCx43 and PCx43 of ischemia-reperfusion myocardium were studied by western blot.Results: Compared with IRI group， the levels of CK-MB and LDH were decreased with significant statistical difference in DPC group(P0.05-P0.01) ; the expression level of Cx43 protein was significantly higher， especially of PCx43(P0.01) ; and left ventricular systolic and diastolic function were increased (P0.05-P0.01) .Conclusions: Diazoxide preconditioning can effectively retain the expression level of Cx43 of left ventricular myocardium caused by ischemia-reperfusion， reduce myocardial injury， and maintain systolic and diastolic function of left ventricle.Cx43 may be involved in the protective effect of diazoxide preconditioning.