Abstract: YiQiFuMai lyophilized injection (YQFM), a modern preparation derived from the traditional Chinese formula Sheng-Mai-San, has demonstrated clinical efficacy in treating heart failure (HF). However, the bioactive constituents responsible for its therapeutic effects and the underlying mechanisms remain incompletely understood. We first demonstrated that YQFM could inhibit endothelial-mesenchymal transition (End-MT), a critical driver of HF pathogenesis. Transcriptomic profiling of human umbilical vein endothelial cells (HUVECs) revealed that YQFM markedly reversed transforming growth factor beta 1 (TGF-β1)-induced transcriptional alterations. Pathway enrichment analysis identified the renin-angiotensin system (RAS) as a key pathway regulated by YQFM, providing transcriptomic evidence for its involvement. This finding guided our subsequent target-based screening of key RAS-related proteins, including angiotensin-converting enzyme (ACE), angiotensin-converting enzyme 2 (ACE2), angiotensin II type 1 receptor (AT1R), and Mas receptor (Mas). Through molecular docking, cellular thermal shift assay (CETSA), microscale thermophoresis (MST), surface plasmon resonance (SPR) and molecular dynamics (MD) simulations, we identified angeloylgomisin O (AO) as the major active constituent with high binding affinity for ACE2. In a coronary artery ligation (CAL)-induced HF mouse model, AO administration improved cardiac function, reduced fibrosis. Further investigations revealed that AO significantly suppressed TGF-β1-induced End-MT in HUVECs, upregulating CD31 and VE-cadherin while downregulating Vimentin, α-SMA, and Slug. Most importantly, AO treatment significantly reversed the suppression of ACE2 in both CAL-induced HF mice and TGF-β1-induced HUVECs. The critical role of ACE2 was corroborated using both agonist and antagonist treatments, which respectively enhanced and attenuated the inhibitory effects of AO on End-MT. These results demonstrate that AO alleviates heart failure primarily through targeting ACE2 and inhibiting End-MT. Our findings provide a mechanistic basis for the clinical application of YQFM and highlight AO as a potential candidate drug for HF.