Objective: To investigate the effects of MDM2 inhibitor SP-141 on proliferation, apoptosis and migration in MGC803 and BGC823 human gastric cancer cells. Methods: The cell viability, proliferation, cell cycle distribution, apoptosis and migration were detected by CCK-8 method, colony formation assay, flow cytometry analysis, Hoechst staining assay and wound-healing assay, respectively. Western Blot was performed to determine the levels of MDM2 and relative biomarkers in SP-141 treated MGC803 and BGC823 cells. Results: The mRNA expressions of MDM2 was significantly increased in gastric cancer tissues compared with adjacent non-cancerous tissues (P< 0.01) in TCGA gastric cancer database. MDM2 expressions did not show obvious differences among five different human gastric cancer cell lines. SP-141 inhibited the cell viability and colony numbers in MGC803 and BGC823, and induced cell cycle arrest at G2/M phase. SP-141 induced cellular apoptosis with down-regulating Bcl-2 as well as up-regulating Bax, cleaved-Caspose-3 and cleaved-PARP1 expressions. SP-141 also suppressed the wound closure in MGC803 cells, and accompanied by the decreased FAK protein expression. Conclusion: The MDM2 specific inhibitor SP-141 effectively suppresses cell proliferation, migration, and promotes apoptosis in human gastric cancer cells.