To observe the effects of Xuefu Zhuyu Capsule (XFZYC), a compound traditional Chinese herbal medicine, on endothelin-1 (ET-1) release in myocardium and vascular endothelium and nitric oxide (NO)/nitric oxide synthase (NOS) system of swines after acute myocardial infarction (AMI) and reperfusion, and to explore the action mechanisms of XFZYC in improving the endothelium function. Forty-five Yorkshire swines were randomized into 3 groups: sham-operated group, untreated group and XFZYC-treated group. A Yorkshire swine model of reperfusion in AMI was established by ligation of left anterior descending coronary artery for 90 min followed by 2 h relaxation. The content of serum ET-1 and NO was measured by radioimmunoassay before and after AMI and after reperfusion, respectively. Twenty-four hours after operation, all Yorkshire swines underwent diagnostic coronary angiography to delineate coronary arteries. The expressions of ET-1 and endothelial nitric oxide synthase (eNOS) in myocardial tissue of ischemic area were quantified with Western blotting. Microvessel density of the implanting sites was assessed by using HE staining. Compared with the untreated group, the levels of serum ET-1 after AMI and reperfusion were significantly decreased in XFZYC-treated group (P<0.01), while the NO levels after AMI and reperfusion in XFZYC-treated group were significantly increased (P<0.01). There was no significant difference in diagnostic coronary angiography between XFZYC-treated group and untreated group (P=0.253). Western blotting showed that the level of ET-1 in ischemic area in XFZYC-treated group was lower than that in the untreated group (P<0.01), while the eNOS protein expression in XFZYC-treated group was higher than that in the untreated group (P<0.01). The results of HE staining and microvessel density analysis of the implanting sites all showed that the degree of telangiectasis was reduced, the cardiac muscle damage was improved, and the density of capillaries was increased obviously in XFZYC-treated group as compared with the untreated group. The endothelium injury may be one of the important mechanisms for no-reflow phenomenon. XFZYC may reduce the no-reflow by protecting endothelium cells.