RNA -methyladenosine (mA) plays a crucial role in regulating gene expression during early embryonic development. However, the mA dynamics at single-nucleotide resolution in preimplantation development remain uncharacterized, and the functional significance of site specific mA modifications in key developmental regulators is largely unknown. Here, using SAC-seq, a single-base resolution, antibody-independent mA profiling method, we generate the first comprehensive mA landscape in bovine oocytes and preimplantation embryos. We identify a previously uncharacterized mA site in RPL12 transcript that is essential for embryonic development. Loss of mA at this site leads to reduced protein synthesis, disrupted expression of translation-related genes, and impaired zygotic genome activation and blastocyst formation. Notably, supplementation with wild-type mRNA fails to rescue the developmental arrest, indicating that mA regulation extends beyond transcript abundance. Our findings provide a valuable resource of mA at single-nucleotide resolution in mammalian embryogenesis and uncover a critical mechanism by which precise, site-specific mA regulates translation and developmental competence in early embryos.