Recent studies have shown that the potential regulatory role of N6-methyladenine (m6A) modification may affect the occurrence and development of various cardiovascular diseases. However, the regulatory mechanism of m6A modification on myocardial ischemia reperfusion injury (MIRI) is rarely reported. A mouse model of myocardial ischemia reperfusion (I/R) was established by ligation and perfusion of the left anterior descending coronary artery, and a cellular model of hypoxia/reperfusion (H/R) was conducted in cardiomyocytes (CMs). We found that the protein expression of ALKBH5 in myocardial tissues and cells were decreased, accompanied by increased m6A modification level. Overexpression of ALKBH5 significantly inhibited H/R-induced oxidative stress and apoptosis in CMs. Mechanistically, there was an enriched m6A motif in the 3′-UTR of SIRT1 genome, and ALKBH5 overexpression promoted the stability of SIRT1 mRNA. Furthermore, results using overexpression or knockdown of SIRT1 confirmed the protective effect of SIRT1 on H/R induced CMs apoptosis. Together, our study reveals a critical role of ALKBH5-medicated m6A on CM apoptosis, supplying an important regulating effect of m6A methylation in ischemic heart disease.