Brief intermittent episodes of ischemia and reperfusion could reduce infarct size, a phenomenon called "postconditioning" at the onset of reperfusion after a prolonged period of ischemia. To investigate whether the opioid receptors and signaling factor JAK-STAT might be responsible for the cardioprotection in ischemic postconditioning, and the possible molecular machinery of cardioprotection. Hundred and twenty healthy New Zealand rabbits were divided into six groups. The myocardial infarct size, cardiac myocyte apoptosis, BCL-2 and P-Stat3 protein expression were tested in the current study. The results suggested that ischemic postconditioning might increase BCL-2 protein expression by activating the opioid receptors and JAK-STAT signaling pathway, and also to reduce ischemia-reperfusion-induced cardiomyocyte apoptosis and to play a key role in myocardial protection. However, further research still needs to be done to unravel the underlying mechanisms.