Objective Aging heart shows significantly reduced tolerance to myocardial ischemia/reperfusion (I/R) injury, so senescent heart is prone to be damaged by the injury. This study was designed to investigate the protective effect of acetaldehyde dehydrogenase 2 (ALDH2) agonist Alda-1 in aging rats after myocardial I/R injury. Methods A total of 40 aging male Sprague Dawley (SD) rats (at an age of 20 to 22 months) were randomized into I/R group (I/R) and Alda-1 group (I/R＋Alda). Another 40 adult rats at an age of 3 to 4 months served as adult control. Rat acute myocardial I/R model was established by ligation of left anterior descending artery for 30min followed by reperfusion for 4h. Alda-1(16mg/kg) and normal saline at the same volume were intravenously infused at a flow rate of 2ml/(kg·h) into the left ventricle of corresponding rats in 5min before reperfusion. The left ventricular pressure was monitored at the same time. At the end of 4 hours reperfusion, ALDH2 activity, reactive oxygen species (ROS) production, and protein carbonylation in the myocardial tissue were measured. Serum level of lactate dehydrogenase (LDH) was tested. Results A significant decrease in ALDH2 activity was observed in the aging hearts, but this effect was blocked by Alda-1. Compared with the adult hearts, myocardial I/R injury was significantly aggravated in aging hearts, which were evidenced by reduced±LVdP/dtmax and increased serum level of LDH (P＜0.05). ALDH2 activator infusion during reperfusion effectively suppressed the above mentioned ischemic injury in the aging hearts (P＜0.05). Furthermore, protein carbonylation and ROS production in the myocardium were increased in the aging hearts compared with the adult hearts (P＜0.05), which was attenuated by Alda-1 treatment. Conclusion Activating myocardial ALDH2 significantly improves the resistance ability to myocardial I/R injury in aging heart. ALDH2-induced cardiac protection may be through suppressing myocardial I/R-induced protein oxidative damage.