Objective: To investigate the miRNA-455-3p expression and its action on proliferation and apoptosis in gastric cancer cells. Methods: The miRNA-455-3p expression levels in normal gastric mucous cell line RGM-1 and five different types of gastric cancer cell lines (AGS, Hs746T, MGC-803, SGC-7901 and BSG-823) were determined by qRT-PCR method. In gastric cancer cells after transfection with miRNA-455-3p mimics, the cell proliferation was measured by CCK8 assay, the apoptosis was assayed by flow cytometry, the expressions of p27 kip1 and p21 were determined by Western blot analysis, and the activities of the caspase enzymes were analyzed by spectrophotometric method, respectively. Results: The miR-455-3p expression levels were significantly decreased in all the five types of gastric cancer cells compared with RGM-1 cells, which was most evident in AGS cells (all P<0.05). in AGS cells after transfection with miR-455-3p mimics, the proliferative ability was decreased, the apoptosis rate was increased, the p27 kip1 protein expression level was up-regulated, and the relative activities of caspase-3 and -9 were increased significantly (all P<0.05), while the p21 protein expression level and caspase-8 activity showed no significant changes (both P>0.05). Conclusion: miRNA-455-3p expression is down-regulated in gastric cancer cells, up-regulating its expression can inhibit proliferation and induce apoptosis in gastric cancer cells and the mechanism may be associated with its increasing p27 kip1 expression and enhancing caspase-3 and -9 activities.