Objective:To investigate the expression of m6A methyltransferase-like protein 3(METTL3)in human osteosarcoma(OS)tissue and the effect of METTL3 on the proliferation and invasion of MG-63 cells.Methods:Quantitative PCR and Western blotting were used to measure the expression level of METTL3 in 5 pairs of human OS tissue samples and investigate the effect of METTL3 on the downstream long non-coding RNA(lncRNA)small nucleolar RNA host gene 5(SNHG5)and the Wnt/β-catenin signaling path-way;methylated RNA immunoprecipitation was used to observe the effect of METTL3 knockdown on the m6A level of lncRNA SNHG5;CCK-8 assay and Transwell assay were used to measure cell proliferation and invasion;Western blotting was used to measure the change in the activity of the Wnt/β-catenin signaling pathway.Results:Compared with the paracancerous normal tissue,human OS tis-sue showed significant increases in the mRNA and protein expression levels of METTL3(P=0.034 and 0.002),and knockdown of METTL3 reduced the m6A level and mRNA expression level of lncRNA SNHG5(P=0.027 and 0.002).Functionally,knockdown of METTL3 inhibited the proliferation and invasion of MG-63 cells(P=0.014 and 0.001)and the protein expression levels of Wnt1,Wnt3a,Wnt10a,β-catenin,and C-myc(all P<0.01),while overexpression of SNHG5 promoted cell proliferation(P=0.027)and inva-sion(P=0.006),activated the Wnt/β-catenin signaling pathway(P<0.01),and reversed the antitumor effect induced by METTL3 knockdown(P<0.01).Conclusion:METTL3-mediated m6A modification of lncRNA SNHG5 promotes the proliferation and invasion of MG-63 cells by activating the Wnt/β-catenin signaling.