Long noncoding RNA UCA1 has emerged as a novel regulator in cancer initiation and progression of various cancers. However, function and underlying mechanism of UCA1 in the progression of gastric cancer (GC) remain unclear. In the present study, we report that UCA1 expressed highly in GC tissues and GC cells, which was partly induced by SP1. UCA1 promoted GC cell proliferation and G1/S transition in vitro and in vivo. Moreover, UCA1 exerted its function through interacting with EZH2, promoting direct interaction with cyclin D1 promoter to activate the translation of cyclin D1. Furthermore, AKT/GSK-3B/cyclin D1 axis was activated to upregulate cyclin D1 due to overexpression of UCA1. In addition, EZH2 and phosphorylated AKT induced by UCA1 could impact each other to form a positive feedback to promote cyclin D1 expression. This study demonstrated that UCA1 as a critical regulator involved in GC proliferation and cell cycle progression by promoting cyclin D1 expression, which indicates that it may be clinically a potential therapeutic target in GC.