To observe the therapeutic effects of Taohong Siwu Decoction on ventricular remodeling and angiotensin type I receptor(AT1) in rats with myocardial infarction.Methods:Model of ventricular remodeling after myocardial infarction was established by ligating the anterior descending coronary artery in wistar rats.After the operation, the rats were randomly divided into a sham operation group, a model group, a Taohong Siwu Decoction low, medium, and high dose treatment group, and a captopril treatment group, with 12 rats in each group.Rats in each group were given continuous administration for 12 weeks.At the end of the treatment, doppler echocardiography was used to evaluate the heart function of the rats, the heart mass/body mass ratio was calculated, and the morphological changes and collagen deposition levels of myocardial tissue were observed by HE and Masson staining.Immunohistochemistry was used to observe the expression of collagen I and collagen Ⅲ.The expression level of AT1 in myocardial tissue were detected by Western Blotting.Results:After coronary artery ligation, rats showed obvious changes in cardiac structure and dysfunction.Compared with the sham operation group, rats in the model group had myocardial tissue damage and interstitial fibrosis.In addition, the left ventricular end systolic diameter(LVESD) and left ventricular end diastolic diameter(LVEDD) in model group were significantly increased(P<0.01), while the ejection fraction(EF) and short-axis contraction rate(FS) was significantly reduced(P<0.01).Heart mass index increased significantly(P<0.01), while collagen content increased(P<0.01).Collagen Ⅰ/Ⅲ expression ratio increased significantly(P<0.01), and AT1 expression level in myocardial tissue was significantly increased(P<0.01).Compared with the model group, each concentration group of Taohong Siwu Decoction and the captopril group can significantly improve the pathological changes of myocardial tissue, increase EF and FS, reduce LVEDD and LVESD, reduce heart weight index, and inhibit excessive collagen in myocardial tissue formation and collagen Ⅰ/Ⅲ expression ratio, while significantly reducing the expression level of AT1 in myocardial tissue(P<0.05 or P<0.01).Conclusion:Taohong Siwu Decoction can significantly reduce myocardial fibrosis after myocardial infarction and improve ventricular remodeling.The mechanism may be related to the inhibitory effect on AT1.