Background: Coronary heart disease (CHD) has become a common cardiovascular disease that seriously threatens the health of people. As reperfusion in the early phase and drug therapy, especially percutaneous coronary intervention (PCI), have become widely used in the clinic, the mortality of acute myocardial infarction in the short term has been reduced significantly. In addition, in 40%-56% of patients who experience myocardial infarction, cardiac dysfunction occurs and about 25%-33% develop heart failure. Methods: This study was designed as a multicenter, double-blind, randomized, placebo-controlled, parallelgroup, superiority trial. Participants were randomly assigned in a 1:1 ratio through a centrally controlled, computer-generated, simple randomization schedule. The primary outcome was left ventricular end-diastolic volume index = left ventricular end-diastolic volume/body surface area. The combined secondary outcomes include traditional Chinese medicine syndrome score, echocardiogram results, 6-minute walk test results, Seattle Angina Questionnaire score, cardiac magnetic resonance imaging results, biological indicators, dynamic electrocardiogram results, and experiment event rate. Assessments will be performed at baseline and at 4, 8, and 12 weeks after randomization. Discussion: This trial will demonstrate that the addition of a Tongmai Yangxin pill (TMYX) to conventional treatment will intervene in the development of cardiac remodeling and cardiac dysfunction.