Background: MicroRNA-630 ( MiR-630) is downregulated in various cancer types, and involved in tumor progression. However, its prognostic value in patients with gastric cancer remains unclear. Methods: Serum samples were collected from healthy individuals and gastric cancer patients. Reverse transcription polymerase chain reaction (RT-PCR) was used to assess miR-630 expression. The diagnostic and prognostic values of miR-630 were analysed by statistical methods. In vitro, miR-630 mimics was transfected into SGC-7901 cells, and the biological function of miR-630 was evaluated by MTT assay, transwell assays, and Western blot. A luciferase assay was used to explore whether SOX4-3'-UTR was a target gene of miR-630. Results: Compared with healthy individuals, gastric cancer patients showed reduced serum miR-630 levels. In addition, miR-630 was expressed at significantly lower levels in patients with aggressive tumors. Interestingly, low miR-630 expression was significantly correlated with poor prognostic and short 5-year survival. Multivariate logistic regression analysis indicated that miR-630 was an independent prognostic factor in gastric cancer. In vitro, miR-630 upregulation resulted in reduced SGC-7901 cell proliferation and invasion. In addition, an inverse correlation between miR-630 levels and SOX4 mRNA amounts was observed in gastric cancer tissues. More importantly, miR-630 upregulation resulted in reduced SOX4 expression, and the luciferase activity of the SOX4-3'-UTR plasmid was significantly suppressed by miR-630. Conclusion: MiR630 is an independent prognostic factor for predicting survival of gastric cancer patients, and may inhibit gastric cancer cell proliferation and invasion, by downregulating SOX4.