Abstract Salvia miltorrhiza Bunge is a traditional Chinese medicine and has long been used for treating liver and heart diseases in China. Salvianic acid A is the main active component of Salvia miltorrhiza Bunge. In the present study, the ability of salvianic acid A in scavenging free radicals, inhibiting lipid peroxidation and mitochondrial membrane permeability transition, as well as respiration and protein thiol oxidation in rat liver mitochondria, was evaluated. The results show that salvianic acid A scavenges superoxide anions in a dose-dependent manner (IC50 52μg/ml). Salvianic acid A could scavenge lipid free radicals and inhibit lipid peroxidation as effectively as Vitamin E. Salvianic acid A also inhibited the mitochondrial membrane permeability transition assessed as the extent of mitochondrial swelling. Salvianic acid A inhibited the oxidation of mitochondrial protein thiols involved in the mitochondrial membrane permeability transitions. We conclude that salvianic acid A is able to reduce lipid peroxidation in the mitochondrial membrane by scavenging free radicals, and inhibit mitochondrial membrane permeability transition by reducing protein thiol oxidation. These data indicated the pharmacological potential of salvianic acid A against pathological processes related to oxidative stress.