Mitochondrial DNA (mtDNA) acts as a damage-associated molecular pattern to activate the stimulator of interferon genes (STING) signaling in macrophages, promoting tissue inflammation. However, its role in acute myocardial infarction (AMI) remains unclear. Macrophage-specific Sting1 knockout mice were used to validate STING's pathological role in AMI. Cardiac and liver mtDNA were used to activate macrophages in co-culture systems with cardiomyocytes to assess fibrosis and hypertrophy. Panaxatriol saponin (PTS) was tested for its ability to block mtDNA-driven macrophage activation and subsequent cardiomyocyte damage. STING-PTS binding ability was analyzed. AMI rats received PTS to evaluate its effects on myocardial inflammation and ventricular remodeling. In vivo, macrophage-specific Sting1 knockout reduced myocardial inflammation and injury after AMI. In vitro, mtDNA-activated macrophages induced cardiomyocyte fibrosis and hypertrophy through STING signaling. PTS suppressed mtDNA-driven macrophage activation by directly binding STING, thereby blocking inflammatory cascades. In AMI rats, PTS treatment attenuated acute inflammation and reversed ventricular remodeling. These findings establish the mtDNA-STING axis in macrophages as a critical driver of post-AMI inflammation and identify pharmacological STING inhibition with PTS as a promising therapeutic strategy. The study bridges genetic validation with translational applications, highlighting macrophage STING as a novel target for ischemic heart disease management.