Objective To observe the expression level of PRMT5 in gastric cancer cells, and explore the effect of knocking down the expression level of PRMT5 on the biological behavior of gastric cancer cells. Methods Western blot was used to detect the expression of PRMT5 protein in gastric cancer cell lines MGC803, SGC7901, MKN45 and human gastric epithelial cells GES-1. siRNA1 and siRNA2 plasmids were transfected to knock down the expression of PRMT5. Cell proliferation and apoptosis assay, transwell assay were used to detect cell proliferation, apoptosis and invasion abilities, respectively. The protein expression levels of β-catenin, cyclin D1 and Bax were detected. Results Compared with GES-1 cells, PRMT5 protein expression levels increased in MGC803, SGC7901 and MKN45 cells (P < 0.001). After knocking down the expression of PRMT5, the cell proliferation and invasion abilities were weakened, the apoptosis rate increased (P < 0.05), the expression of β-catenin and Cyclin D1 protein decreased, and the expression of Bax protein increased (P < 0.001). Conclusion The expression level of PRMT5 is increased in gastric cancer cells. Knockdown of PRMT5 expression level could inhibit cell proliferation, invasion and promote cell apoptosis via reducing Wnt/β-catenin signaling pathway.