AIM: To compare the effects of crocetin and crocin on myocardial injury in rats. METHODS: In vitro, the myocardial cells injured by low glucose and hypoxia were treated with serum from rats given crocetin (50 mg·kg -1)or crocin(150 mg·kg-1). The levels of LDH, CK, MDA and SOD in culture medium were measured and the cell activity was detected by MTT. In vivo, a rat myocardial ischemia model was set up using the coronary ligation technique. J point shift and T wave change in the electrocardiograph (ECG) in 6 hours after the treatment and area of myocardial infarction were assessed. The histopathological change of myocardium was observed by HE staining. The serum samples were collected to measure the levels of LDH and CK. RESULTS: In vitro, serum containing crocetin decreased the levels of LDH ,CK and MDA, increased the level of SOD and the activity of cardiac myocytes. However, serum containing crocin showed no significant protective effect. Compared to the model group, crocetin downshified the J point and T wave in the ECG evaluation, decreased the levels of serum LDH and CK and the area of the myocardial infarction. Crocetin reduced the histopathological changes caused by myocardial injury. CONCLUSION: ig crocetin can significantly protect the injured myocardial cell both in vivo and in vitro while ig crocin can not. So, it is suggested that crocetin by oral administration is suitable to cure myocardial ischemia in clinical practice, while crocin by oral administration is not.