N(6)-methyladenosine (m(6)A) modification is an important mechanism in microRNA processing and maturation. Previous studies show the involvement of pri-miRNA methylation in regulating the occurrence and development of tumor-related diseases. In this study, we investigated the role of its aberrant regulation in cardiac diseases. Myocardial infarction (MI) mouse were established by ligation of the left anterior descending branch of the coronary artery. We showed that the expression of methyltransferase 14 (METTL14) was significantly increased in myocardium of MI mice. We demonstrated that METTL14 methylated the primary transcript miRNA (pri-miR-5099), promoting the recognition by DiGeorge critical region 8 (DGCR8) and the maturation processing of pri-miR-5099. Mature microRNA-5099-3p (miR-5099-3p) inhibited the expression of E74 like ETS transcription factor 1 (ELF1), which transcriptionally regulated pyroptosis factors such as acysteinyl aspartate-specific proteinase 1 (caspase-1) and gasdermin D (GSDMD), ultimately leading to cardiomyocyte pyroptosis. This study reveals that myocardial infarction-induced miR-5099-3p excessive maturation via m(6)A modification promotes the development and progression of cardiomyocyte pyroptosis.