Objective To preliminarily explore the effects of human microRNA-181a on migration of gastric cancer cells and its mechanism. Methods The expression of miRNA-181a-5p in gastric cancer cell line GC9811 and peritoneal high metastasis gastric cancer cell line GC9811-P were tested by quantitative real-time polymerase chain reaction (qRT-PCR). GC9811 cell line was transfected by endogenous synthetic analog mimic and its homologous negative control of miRNA-181a-5p, which were considered as up-regulated group and its control group respectively; GC9811-P were transfected by miRNA inhibitor and its homologous negative control of miRNA-181a-5p, which were considered as down-regulated group and its control group respectively. After miRNA-181a-5p was up or down-regulated, cell proliferation, migration and apoptosis capabilities of gastric cells were detected by matrix thiazolyl tetrazollium (MTT) assay, cloning-forming assay, Transwell migration test, wound healing assays and apoptosis test. After miRNA-181a-5p was up or down regulated, the changes of matrix metalloproteinase (MMP) 14 expression were determined by Western blot. Independent sample t test was performed for mean comparison between samples and chi square test was used for rate comparison. Results The results of qRT-PCR showed the relative expression quantity of miRNA-181a-5p in GC9811 was 1.000 00±0.021 26 and in GC9811-P was 3.175 61±0.106 76, and the difference was statistically significant (t=34.620, P 0.05). The results of Western blot showed that the grey value of up-regulated group was 561.881±35.740, which was higher than that of up-regulated control group (275.784±23.520); that of down-regulated group was 579.565±37.950, which was lower than that of down-regulated control group (1 312.760±51.270), and the differnces were statistically significant (t=11.580 and 19.910, both P<0.01). Conclusion miRNA-181a-5p highly expresses in peritoneal high metastasis gastric cancer cell line GC9811-P and promoted the proliferation and migration of gastric cancer cell line GC9811 and GC9811-P with a tendency to suppress apoptosis. Key words: Stomach neoplasm; Proliferation and migration; miRNA-181a-5p; Matrix metalloproteinase 14