Objective: To observe the effects of Tongguan Capsule ((sic), TGC) on post-myocardial infarction ventricular remodeling and heart function in rats. Methods: A rat model of acute myocardial infarction (AMI) was established by coronary ligation. Experimental rats were randomized to 4 groups including three model groups (Group A: captopril 5 mg/kg.day, n=7; Group B. TGC 10 g/kg.day, n=7; and Group C: placebo, n=8), and a sham-control group (Group D. blank control, n=6). Animals were treated for 4 weeks. The cardiac function of rats was assessed at the end of the experiment based on left ventricular ejection fraction (LVEF) and left ventricular short axis fractional shortening (LVFS) detected by colored echocardiography; meanwhile, the condition of ventricular remodeling was observed through the levels of left ventricular mass (LVM), plasma aldosterone (ALD), myocardial angiotensin II (Ang II) and myocardial collagen measurements. Results: At the end of the experiment, LVEF and LVFS in Group A and B were improved significantly, while those in Group C were unchanged, the LVEF in Group A, B, C, and D was 0.57 +/- 0.46, 0.61 +/- 0.08, 0.36 +/- 0.55 and 0.76 +/- 0.02, respectively; and their LVFS was 0.31 +/- 0 52, 0.34 +/- 0.04, 0.23 +/- 0.57 and 0.45 +/- 0.03, respectively. The difference was statistically significant when comparing the two indexes in Group A and B with those in Group C and D (P<0 05). LVM, levels of plasma ALD and myocardial Ang II were lower in Group A and B than in Group C, but a comparison between Group A and B showed an insignificant difference in lowering LVM and ALD, while the lowering of Ang II was more significant in Group B than in Group A (754 7 +/- 18.7 pg/mL vs 952.6 +/- 17 6 pg/mL, P<0.05). Morphological examination showed that in Group A and B the swollen myocardial cells had shrunk, with regularly arranged myocardial fibers and decreased collagen proliferation, but the improvements in Group B were more significant. Conclusion. TGC could markedly improve the post-infarction ventricular remodeling and cardiac function in rats, showing that the efficacy was better than or equal to that of captopril.