Abstract: Objective To investigate the protective effects of tea polyphenols (TP) against myocardial ischemia/reperfusion (IR) injuries and explore the possible mechanisms. Methods Langendorff-perfused rat hearts were subjected to ischemia for 30 min followed by reperfusion for another 30 min. Myocardial function indices were measured by a left ventricular cannula via a pressure transducer connected to the polygraph in isolated Langendorff hearts and energy metabolism was measured using 31P nuclear magnetic resonance (NMR) spectroscopy. Whole-cell patch-clamp technique was used to record calcium inward current (ICa-L) in cultured rat cardiac myocytes. Results Compared with the control hearts, the ex vivo rat hearts with 2.5 mg/L TP treatment showed significantly increased left ventricular developed pressure (LVDP), maximal rise rate of LVDP (+ dp/dtmax), maximal fall rate of LVDP (-dp/dtmax), and coronary flow (CF) (P<0.05). During both cardiac ischemia and reperfusion phase, ATP and PCr levels were elevated significantly in TP-treated hearts compared with those in the control hearts (P<0.05). In cultured rat cardiac myocytes, ICa-L was remarkably decreased by TP at the doses of 2.5 and 5.0 mg/L (P<0.01). Conclusion Our results support a possible protective role of TP against myocardial IR injury by improving myocardial energy metabolism and inhibiting ICa-L in the cardiac myocytes.