miR-551b has been reported to be involved in tumorigenesis, cell invasion, and metastasis in gastric cancer but the mechanism remains unclear. In this study, in an attempt to address this question, we examined expression of miR-551b in gastric tumors and adjacent normal tissue. We transfected SGC-7901 gastric cancer cells with miRNA non-sense sequences (NC group), miR-551b mimics (miR-551b mimic group), and miR-551b inhibitors (miR-551b inhibitor group) to investigate the role of miR-551b in autophagic apoptosis. In gastric tissue, our real-time PCR results revealed that expression of miR-551b was significantly downregulated and the relative expression of miR-551b (1.75 +/- 0.13) was significantly lower than in normal tissue (2.47 +/- 0.38) (P<0.05). In transfected SGC-7901 cells, compared with the NC and miR-551b inhibitor group, miR-551b expression level and apoptosis rate in miR-551b mimics group was significantly increased whereas proliferation and invasion rates were significantly decreased (P<0.05). Hoechst 33342 fluorescence staining showed that a large number of autophagosomes were detected in miR-551b mimic group, fewer in the NC group, and only a small number in miR-551b inhibitor group. Western blotting showed that expression levels of NF-kappa B, LC3 II, and Beclin 1 in miR-551b mimics group were significantly higher than in the NC group and miR-551b inhibitor group (P<0.05). Our findings suggest that miR-551b could inhibit proliferation, apoptosis, and invasion of gastric cancer cells and the action mechanism may be related to induction of gastric cancer cells autophagic apoptosis.