Gastric cancer (GC) is a high mortality disease. We studied the function and mechanism of long non-coding RNA prostate cancer-associated transcript 6 (lncRNA PCAT6) on cell proliferation and epithelial-mesenchymal transition (EMT) in GC cells. CCK-8, flow cytometry and colony formation assay were respectively used to detect the cell viability, apoptosis and colony formation. PCAT6 and miR-15a expression were changed by cell transfection. Moreover, the level of Cyclin D1, p53, Bax, Cleaved caspase-3 and relate-proteins of EMT and cell pathways were investigated by Western blot. Besides, the level of miR-15a and PCAT6 was tested by RT-qPCR. Besides, the target relation between miR-15a and PCAT6 were tested by luciferase assay. PCAT6 was highly expressed in GC cells and tissues. Silencing of PCAT6 restrained the relate-proteins of cell proliferation and EMT. Furthermore, PCAT6 reversely regulated miR-15a and miR-15a inhibitor reversed the efficacy of sh-PCAT6 in cell proliferation and EMT. PCAT6 restrained the relate-proteins of RB/E2F and Wnt/β-catenin pathways and miR-15a reverse this progress. Finally, PCAT6 was a target of miR-15a. Silencing of lncRNA PCAT6 restrained proliferation and EMT of GC cells by targeting miR-15a via RB/E2F and Wnt/β-catenin pathways.