Reperfusion injury has been one of the serious problems in cardiac surgery and medicine. We report a novel method of myocardial protection. Eight Sprague-Dawley rats, group A, were administrated green tea polyphenol orally. Eight other rats, group B, received no medication. Isolated hearts were perfused with a Langendorff's apparatus, and reperfused after 90min arrest. The left ventricular (LV) function, size, weight and the oxidative stress spaciotemporal analysis were performed. The LV size in group B became enlarged by 1.8+/-0.12 (mean+/-SD), but in group A, the LV enlarged only 1.1+/-0.08 times. The heart weight ratio was lighter (1.35+/-0.05) in group A than in group B (1.49+/-0.03, P<0.05). The LV end-systolic pressure volume relationship remained higher in group A. Oxidative stress as shown by 8-hydroxy-2'-deoxyguanosine was lower in group A (81.5+/-11.6) than in group B (226.9+/-35.6, P<0.0001). Polyphenol labeled FITC was located in the cell membrane of cardiomyocite. Polyphenol can protect a heart from oxidative stress, and maintain good LV function after ischemic arrest and reperfusion. This pre-treatment by polyphenol may add further benefit to current treatments of myocardial protection.