The formation of long-term memory is critical for learning ability and social behaviors of humans and animals, yet its underlying mechanisms are largely unknown. We found that the efficacy of hippocampus-dependent memory consolidation is regulated by METTL3, an RNA N6-methyladenosine (m6A) methyltransferase, through promoting the translation of neuronal early-response genes. Such effect is exquisitely dependent on the m6A methyltransferase function of METTL3. Depleting METTL3 in mouse hippocampus reduces memory consolidation ability, yet unimpaired learning outcomes can be achieved if adequate training was given or the m6A methyltransferase function of METTL3 was restored. The abundance of METTL3 in wild-type mouse hippocampus is positively correlated with learning efficacy, and overexpression of METTL3 significantly enhances long-term memory consolidation. These findings uncover a direct role of RNA m6A modification in regulating long-term memory formation, and also indicate that memory efficacy difference among individuals could be compensated by repeated learning.