Objective To observe the effect of Zhuangtongyin on the expression of ET-1 in serum and myocardium of rats with myocardial ischemia and blood stasis syndrome， and to explore the protective mechanism of Zhuangtongyin on myocardial ischemia in patients with coronary heart disease. Methods Rat model of myocardial ischemic blood stasis was established by left coronary artery ligation. The rats were randomly divided into blank， sham operation group， model group， Zhuangtongyin low dose（6.8g/kg）， medium（13.6g/kg）（27.2g/kg）and positive control group 7 groups. After 4 weeks of intragastric administration， the expression of ET-1 in serum and myocardium was detected by enzyme-linked immunosorbent assay（ELISA） and WB（Western blotting）. Results Serum ELISA results showed that， Compared with the blank group and the sham operation group， the expression of ET-1 in the model group was significantly increased（P<0.05）， after treatment， ET-1 could decrease ET-1， but the effect of ET-1 was lower in middle dose group（P<0.05）. WB results showed that， the mean gray value of ET-1 in model group was significantly higher than that in blank group， sham operation group， after the intervention， the average gray value of ET-1 was decreased， but the effect of the middle dose group was the most obvious. Conclusion Zhuangtong can reduce the expression of ET-1 in rats with myocardial ischemia and blood stasis syndrome ， alleviate vasoconstriction， and protect the myocardial ischemia in rats.