18 beta-Glycyrrhetinic acid (18 beta-GA) is a component extracted from licorice. This study aimed to evaluate the effects of 18 beta-GA on isoproterenol (ISO)-induced acute myocardial infarction in rats and mice. Two consecutive days of subcutaneous injection of ISO (85 mg/kg/day) resulted in acute myocardial infarction. We examined the pathological changes, oxidative stress, inflammatory response, and expression of apoptosis in mouse hearts. The expressions of phosphoinositol-3-kinase (PI3K), protein kinase B (Akt), and the phosphorylation levels of PI3K (p-PI3K) and Akt (p-Akt) were determined by western blotting. The whole-cell patch-clamp technique was applied to observe the L-type Ca2+ currents, and the Ion Optix detection system was used for cell contraction and Ca2+ transient in isolated rat cardiac ventricular myocytes. In ISO-induced myocardial infarction, the J-point, heart rate, creatine kinase, lactate dehydrogenase, superoxide dismutase, catalase, malondialdehyde, glutathion, and reactive oxygen species decreased in mice after 18 beta-GA treatment. 18 beta-GA improved ISO-induced morphologic pathology, inhibited the inflammatory pathway response and cardiomyocyte apoptosis, and inhibited PI3K/Akt signaling. 18 beta-GA could significantly inhibit ICa-L, myocardial contraction, and Ca2+ transient. This study demonstrates that 18 beta-GA has cardioprotective effects on acute myocardial infarction, which may be related to inhibiting oxidative stress, inflammation, apoptosis via the PI3K/Akt pathway, and reducing cell contractility and Ca2+ concentration via L-type Ca2+ channels.