〔Abstract〕 Objective To investigate the effect and mechanism of methyltransferase-like3(METTL3),which functions as m6A modification methyltransferase,on the cellular proliferation,clone formation and migration of nonsmall cell lung cancer(NSCLC) cells.Methods The METTL3 level and patient overall survival were analyzed by bioinformatics.In the transfected A549 cells,the expression of METTL3 was detected by RT-PCR and Western blot assays,the m6A level was detected by m6A RNA Methylation Assay kit,the cellular viability and growth were detected by CCK-8 assay,the apoptosis was detected by immunofluorescent assay,the colony growth was detected by clone formation assay,the cell migration growth was detected by scratch.Results Bioinformatics showed that METTL3 was highly expressed in NSCLC and negatively correlated with patient overall survival.The RT-PCR and Western blot data showed that the METTL3 level was higher in NSCLC cells.Moreover,higher METTL3 significantly promoted m6A level,cell proliferation,colony formation,migration,inhibited cell apoptosis,increased the mRNA and protein expressions of EMT-related marker Vimentin but inhibited apoptosis and decreased the mRNA and protein expressions of EMT-related marker E-cadherin in the A549 cells.Furthermore,the contrasting results were obtained in the A549 cells with the knockdown of METTL3.Conclusion The over-expressed METTL3 increases the m6A levels in NSCLC cells and promotes cellular proliferation,colony formation,and migration growth,thereby laying a theoretical foundation for future research on early diagnosis and targeted drug development for NSCLC by targeting METTL3.