Abstract: AIM　To study the influence of a novel K_ATP channel opener JTV-506(JTV) on cardiac function and myocardial infarct size of isolated rat heart. METHODS　The Langendorff apparatus was used to study the effect of JTV at different concentrations on the flow of coronary artery and the pressure of left ventricle. The effect of JTV on infarction size was observed on the isolated rat double coronary arteries perfusion model. RESULTS　JTV 1 μmol.L^-1 increased the flow of coronary artery obviously. When the concentration reached 10 μmol.L^-1, JTV decreased the systolic pressure of the left ventricle. JTV 1 μmol.L^-1 reduced the myocardial infarct size whether it was administrated during both preischemic and ischemic period or only during ischemic period. This effect was completely blocked by glibenclamide, but when glibenclamide was administrated alone, it showed no obvious effect on infarct size. CONCLUSION　The K_ATP channel opener JTV can obviously dilate coronary artery and decrease cardiac systolic function when administrated at high doses. JTV was found to decrease the infarct size when administrated in doses that did not affect cardiac function. These effects were related to the opening of K_ATP channel.