Objective: To compare the effect o f crocin and crocetin on isoprotereno-l induced myocardial injury and ischemia in prime cultured cardiacmyocytes of rats. Methods: An in vitro injury model of rat neonatal cardiacmyocytes was induced by ISO ( 1 mm/L- 1 ). Cells were treated with serum from rats given crocetin(50, 25 mg/kg- 1 ) o r crocin( 150 mg/kg- 1 ) for 48 h. The level of creatine phosphokinase( CK ) and lactic dehydrogenase( LDH) in culturemedium were measured and the cell activity was detected by MTT assay. In addition, myocardial ischemia was induced by ISO ( 40mg/kg- 1 for two days, once a day, sc) in vivo. The rats were randomly ig crocetin or crocin. Subsequently, J point shift and T wave change were assessed in the electrocardiograph ( ECG) after the treatment. Cardiac indexes were examined. The level of LDH, CK, malondialdehyde (MDA ) and superoxide dismutase(SOD) w ere measured. The histopathological change of myocardial was investigated by HE staining. Results: Compared with model group, crocetin contained serum reduced change o f beating frequency and leakage of LDH and CK, and protected the activity o f cardiacmyocytes. Crocetin ( ig ) downshifted the J point and T wave change, obviously decreased the level of LDH and CK in plasma and the content of MDA in heart tissue and increased the activity of SOD. The histopathological changes confirmed the protective effect of crocetin on the myocardial injury. However, ig crocin gave no significant improvement of isoproterenol-induced myocardial injury. Conclusion: Crocetin (ig) can improve isoproterenol-induced myocardial injury in vitro and in vivo while ig crocin cannot. It is suggested oral administration of crocetin can be used to cure myocardial ischemia in clinic, while crocin of oral administration is not suitable for this use.