BACKGROUND Microrna-155 plays an important role in the pathogenesis, progression and treatment of various cancers. It is abnormally expressed in gastric cancer, but its expression level, mechanism and significance are controversial in different studies. So we make the study to explore the expression level, significance and mechanism of microRNA-155 on gastric cancer. METHODS Target genes of microRNA-155 in TargetScan and mirDB databases were analyzed by Wayne Mapping, Enrichr database, String database, TIMER database. Forty-three pairs of cancer tissues and adjacent tissues were collected to extract total RNA and protein. Expression of MicroRNA-155, Rictor, Fos, Beclin1, LC3, caspase3 and caspase9 were measured by qRT-PCR and western blot. The relationship between gene expression and clinicopathological factors were analyzed. SPSS 23.0 was used for statistical analysis. RESULTS A total of 700 (miRDB) and 556 (TargetScan) target genes were obtained and 280 genes were in the intersection of Wayne Mapping, 49 of them had a target score of 90 or more. GO and KEGG analysis revealed that they were related to autophagy or apoptosis pathway. Rictor and Fos were selected as research objects. Thirty-two cases showed high microRNA-155 expression (group H) and 11 cases showed low expression (group L). Twelve patients had high Rictor expression and 31 patients had low expression; Thirteen cases had roughly normal Fos expression and 30 cases had low or negative expression; Thirty-three cases had high Beclin1/LC3 expression and 10 cases had low expression; Ten cases had high caspase3/caspase9 expression and 33 cases had low expression. According to the results of immunohistochemistry and western blot, Rictor, Fos, caspase3 and caspase9 were low expressed while Beclin1 and LC3 were high expressed in group H. However, all the six genes had no significant difference in group L. CONCLUSIONS The abnormal expression of microRNA-155 may indicate the occurrence of gastric cancer and its expression level is negatively correlated with clinical stage of cancer. The down-regulated expression of Rictor and Fos, enhancement of autophagy and weakening of apoptosis may be related to the over-expression of microRNA-155. MicroRNA-155 may promote the progression of gastric cancer by promoting autophagy and inhibiting apoptosis.