Objective:To investigate the effects of dexmedetomidine preconditioning on mitochondrial function of myocardial ischemia reperfusion injury(MIRI),and to explore the protective effect of dexmedetomidine preconditioning on myocardium with ischemia and reperfusion injure. Methods:A total of 30 healthy male Sprague Dawley(SD)rats,aged 8 weeks,were randomly divided into three groups:the sham operation group(group A),the myocardial ischemia-reperfusion group(group B),and the dexmedetomidine preconditioning group(group C). The model of myocardial ischemia reperfusion injury was performed by ligation of the left anterior descending coronary artery. Cardiac functions were detected by echocardiography. The expression of the mRNA levels associated with mitochondrial function was performed by real-time PCR. Ultrastructure of myocardial mitochondria was observed under electronic microscope. Results:Compared with group A,the cardiac function of group B and group C were markedly decreased;the mRNA levels of genes related to mitochondrial function were significantly lower in group B and group C than that in group A(P <0. 05). Compared to group B,the cardiac function of group C was enhanced;the mRNA levels of genes related to mitochondrial function were higher in group C than in group B(P < 0.05). We also found that impaired mitochondrial ultrastructure was observed in group B. Compared with group B,impaired mitochondrial structure was significantly improved in group C. Conclusion:Dexmedetomidine preconditioning could improve mitochondrial function to alleviate myocardial ischemia reperfusion injury.