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Background/Aims The purpose of this study is to explore the inhibition or activation effects of microRNA-146 B on the expression of PTP1B in gastric cancer cells. Methods The expressions of PTP1B and miR-146b in gastric cancer were detected by RT-qPCR. The effects of miR-146b on cell apoptosis and proliferation of gastric cancer were detected. The methods used in the detection process included Annexin V/PI dying method, colony formation assay, and MTT assay. The downstream target gene miR-146b was predicted and screened by bioinformatics and luciferase reporter assay. The mRNA and protein expressions of the target gene PTP1B miR-146b were determined using RT-qPCR and western blot. The expression of miR-146 B in mice was detected by the cells transfected with microRNA-146 B in vivo. Results Compared with normal tissues, PTP1B was higher and miR-146b was lower in cancer cells. Over-expression of miR-146b can inhibit cell viability and increase the apoptosis rate. According to the luciferase reporter assay, PTP1B was the downstream target gene of miR-146b. The re-introduction of PTP1B reversed the growth inhibition and apoptosis of gastric cancer cells induced by miR-146b. From the mouse xenograft model, the over-expression of miR-146b inhibited the tumor growth and reduced the expression level of PTP1B. Conclusion miR-146b directly inhibits the expression of PTP1B and suppressed the growth and development of gastric cancer.