Background: Chemoresistance severely deteriorates the prognosis of advanced gastric cancer (GC) patients. Several studies demonstrated that H. pylori (HP)-positive GC patients showed better outcomes after receiving chemotherapy than HP-negative ones. This study aims to confirm the role of HP in GC chemotherapy and to study the underlying mechanisms. Methods: The HP infection co-culture with GC cell lines were performed. The m(6)A-seq and NGS were used for bioinformatic analysis. Western Blot, qRT-PCR and IHC were adopted for expressions of METTL3, BRD2 and YTHDF2. The ATPGlow, flow cytometry and IF were used to detect the cell viability, DNA damage, apoptosis and pyroptosis. Luciferase reporter assay and CHIP were applied to explore the mechanisms. Results: The HP infection sensitized GC cells to 5-FU and induced expressions of METTL3 and YTHDF2. The HP infection promoted transcription of METTL3 through NF-κB pathway, therefore promoting the m(6)A modification level. METTL3 induced the m(6)A modification of BRD2 while YTHDF2 promoted the decay of mRNA of BRD2, both of which could promote the apoptosis and pyroptosis induced by 5-FU. In addition, BRD2 regulated the transcription of FLIP by importing FOXO4 into nucleus, thereby inhibiting the activation of Caspase-8, which was considered as the molecular switch of both apoptosis and pyroptosis. Conclusions: HP-induced m(6)A methylation could sensitize gastric cancers to 5-FU with activation of caspase-8 and induced apoptosis and pyroptosis. The Methylated BRD2 activated by NF-κB pathway regulates Caspase-8 by binding to FLIP-promoter FOXO4. This study provides new sights to the HP-positive gastric cancer chemotherapy.