Objective: To investigate the inhibitory effect of thioridazine on growth of gastric cancer cells in vitro and the mechanism. Methods: Gastric cancer SGC-7901 cells were exposed to different concentrations of thioridazine for 24 hours, and then the proliferation and apoptosis of the gastric cells were detected by MTT assay and flow cytometry, and the expressions of apoptosis-related proteins that included bax, bcl-2 and caspase-3 were measured by Western blot analysis, respectively. Results: In SGC-7901 cells after exposure to thioridazine, the proliferation was decreased, apoptosis was increased significantly, the expression of antiapoptotic protein bcl-2 was down-regulated, and proapoptotic protein bax as well as caspase-3 was up-regulated significantly, and all effects showed a concentration-dependent manner (all P<0.05). Conclusion: Thioridazine has evident inhibitory effect on human gastric cancer in vitro, which may possibly be associated with its activating the caspase-3-dependent apoptotic pathway.