Background and Aims The colonization of Helicobacter pylori (HP) in the human stomach is a recognized risk factor for the occurrence of gastric cancer. Study also found that the oxidative stress is significantly changed in gastric cancer cells after HP infection, while the mechanism is not entirely elucidated. Therefore, this study was conducted to investigate the potential mechanism and role of HP-induced oxidative stress in gastric cancer cells.Methods In gastric cancer SNU-1 cells after HP infection, the changes in production of reactive oxygen species (ROS) and proliferation ability were detected by DCF-DA fluorescence and CCK-8 assay. The key genes inducing oxidative stress in SNU-1 cells after HP infection were identified by high-throughput sequencing and siRNA screening, and then the key upstream miRNAs causing oxidative stress in SNU-1 cells were identified using miRDB online analysis tools and luciferase reporter assay, in combination with gain- and loss-of-function experiments for validation.Results In SNU-1 cells after HP infection, the ROS level was increased and the proliferation ability was enhanced, but these changes were abolished by simultaneous treatment with the ROS inhibitor acetylcysteine (all P>0.05). The results of siRNA screening found that the ROS level was increased and the proliferation ability was enhanced in SNU-1 cells with HP infection after peroxiredoxin 2 (PRDX2) knock-down and the opposite changes were found after PRDX2 overexpression (all P<0.05). Meanwhile, Western blot validation showed that PRDX2 was down-regulated in SNU-1 cells after HP infection. The promoter activity of PRDX2 in SNU-1 cells did not change after HP infection (P>0.05), but the mRNA level of PRDX2 was decreased (P<0.05). Results of analysis showed that the expression level of miR-650 in SNU-1 cells with HP infection was increased (P<0.05), and miR-650 targeted at the 3' non-coding region of the PRDX2 mRNA. Results of validation showed that the PRDX2 expression was down-regulated, the ROS level was increased and the proliferation ability was enhanced in SNU-1 cells after overexpression of miR-650, and the opposite changes were seen after miR-650 knockdown (all P<0.05); the proliferation ability had no significant change in SNU-1 cells with HP infection and simultaneous miR-650 knockdown or simultaneous PRDX2 overexpression (both P>0.05).Conclusion The mechanism and action of HP infection in gastric cancer cells is possibly that it up-relates the expression of miR-650, and the latter suppresses the mRNA and protein expressions of PRDX2 by binding its 3' non-coding region, and then causes the increase of ROS level, thereby promotes the proliferation of gastric cancer cells.