AIM To study the protective effects of xanthones: 1,8 dihydroxy 3,5 dimethoxyxanthone(Xan Ⅰ); 1 hydroxy 3,5 dimethoxyxanthone(Xan Ⅱ);1 hydroxy 3,7,8 trithoxyxanthone(Xan Ⅲ) from Canscora lucidissima on ischemia reperfusion injury exaggerated by activation of Na +/H + exchange system. METHODS The perfused isovolumic contracting rat hearts were subjected to 20 mmol?L -1 NH 4Cl loading for promoting the Na +/H + exchange in the model of ischemic reperfusion injury and the protective effects being pretreated with Xans on the injury were examed. RESULTS Xans could relieve the effects: activation of Na +/H + exchange inhibited the recovery of ventricular function significantly, and exacerbated the myocardial injury as evidenced by increase in release of LDH, associated with the accumulation of intracellular Na +,Ca 2+ and the loss of intracelullar K +. CONCLUSION Xans has the protective effects on ischemic reperfusion injury exacerbated by activation of Na +/H + exchange system.