Objectives: This study examined the effects of salvianolic acid B (SAB) on exhaustive exerciseinduced cardiac muscle damage to rats.\nMethods: The study was carried out with 12-week-old young adult male Sprague-Dawley rats. Thirty-six rats were divided into 3 groups; normal (n=12), exhaustive exercise group (ExS, n=12) and exhaustive exercise with SAB (ExS+SAB, n=12). Five days before exhaustive exercise, SAB were medicated for 5 days in ExS+SAB group. Rats in ExS and ExS+SAB group were forced to swim for 150 minutes and then they were sacrificed, while rats in normal group were sacrificed at rest. After that, blood was collected and cardiac muscle tissue damage indices were analyzed.\nResults: Serum aspartate transaminase activity and lactate dehydrogenase activity were significantly lower in ExS+SAB group than in ExS group. Serum creatine phosphokinase activity of ExS+SAB was significantly lower than ExS group. However, the content of serum creatinine had no difference between ExS and ExS+SAB group. In the H&E stained left ventricle myocardium, ExS group showed signs of myocardial damage such as sporadic fragmentation of myocardial fibers, interstitial edema, cytoplasmic eosinophilia and neutrophils infiltration. However, ExS+SAB group alleviated the severity of the signs of myocardial damage. In the myocardial dihydroethidium staining, optical density was remarkably decreased in ExS+SAB group compared to ExS group. Furthermore, the up-regulation of Bax/Bcl-2 ratio was observed in ExS+SAB group compared with ExS group.\nConclusions: The above results suggest that SAB may protect cardiac muscle damage via antioxidant activity and prevention of apoptosis.