Aim To study the effects of L-carnitine against ischemic/reperfusion injury in vivo rabbits cardiomyocyte and its possible mechanism. Methods Myocardial ischemic/reperfusion models were built in healthy new Zealand rabbits.Rabbits were subjected to 30 min myocardial ischemia followed by reperfusion for 3 h.Anesthetized rabbits were randomly divided into 3 groups: blank control group(n=5)in which left anterior descending coronary artery was exposed and a piece of silk thread was placed around the artery but not tied;saline control group(n=10) in which normal saline was injected into sublingual vein after MI 30 min;L-carnitine group(n=10) received intravenous Lcarnitine 3.0 g and saline 250 mL after MI 30 min.ECG throught the experiment, free fatty acid(FFA),superoxide(SOD),malonaldehyde(MDA),creatine kinase(CK),Na~+-K~+-ATPase and Ca²⁺-Mg~(2+)-ATPase were all observed after reperfusion.The content of Heart shork protein 70 obstained below ischemia/ reperfusion region 5 mm through myocardial layment was determined by western blot. Results Compared with blank control group or saline control group,L-carnitine group showed protection against MI/R injury as evidenced by more effective improvement in ST of ECG,marked increase of Na~+-K~+-ATPase,Ca²⁺-Mg~(2+)-ATPase,SOD;and marked decrease of FFA and MDA.The content of CK has tendency of decline.The content of HSP 70 was dramatically increased((p<0.05)). Conclusions L-carnitine can protect cardiomyocyte from ischemic/reperfusion injury through many aspects by inducing HSP70.