OBJECTIVE To investigate the effects of Corocalm (shuguan capsule) on acute myocardial ischemia in anesthetized dogs and its possible therapeutic mechanism. METHODS The acute ischemia model was established by ligating the left anterior descending (LAD) artery. Twenty-five dogs were randomly divided into 5 groups (5 dogs in each group): the control group (treated with normal saline 3 mL/kg), the refined Guanxin Capsule group (GXC 200 mg/kg), high and low dose Corocalm groups (48.5 mg/kg for low dose group and 194.0 mg/kg for high dose group) and the Diltiazem group (5 mg/kg). The animals were treated via a single duodenal administration after the model was established. The experiments used epicardial electrocardiogram (EECG) to measure the scope and degree of myocardial ischemia. Simultaneously, the coronary blood flow (CBF) and serum activity levels of creatine phosphokinase (CK) and lactate dehydrogenase (LDH) were measured by electromagnetic flow meter and automatic biochemical analyzer respectively. The plasma endothelin (ET) content was quantified by radioimmunoassay. RESULTS Corocalm (48.5 mg/kg and 194.0 mg/kg) significantly decreased the degree and scope of myocardial ischemia, reduced the infarct area, markedly increased the CBF, and inhibited the increase of CK and LDH activities and ET levels induced by myocardial ischemia/infarction. CONCLUSIONS Corocalm could improve the state of acute myocardial ischemia and infarction in dogs. The mechanism of action might be correlated to increasing CBF, inhibiting CK and LDH activities and preventing ET release.