Objective:To investigate the effects of melatonin on adhesion and migration abilities of human SGC-7901 gastric cancer cells and its role in reorganization of actin cytoskeleton. Methods:SGC-7901 cells were treated with different concentrations of melatonin for 24h. The contents of G-actin(in cytosolic fraction)and F-actin(in cytoskeletal fraction)in cells were measured by Western blot. Cellular F-actin stained with FITC-phalloidin was examined by fluorescence microscopy. Adhesive assay was used to detect the adhesive ability of SGC-7901 cells to HUVECs. Migration rate was measured by wound healing assay. Results:After treated with melatonin for 24h,the celluar F-actin was depolymerized and actin cytoskeleton was rearranged. Consistently,the abilities of adhesion and migration in SGC-7901 cells were significantly reduced compared to the control cells. Conclusion:Melatonin inhibits the abilities of adhesion and migration in SGC-7901 cells,which may be via reorganization of cellular actin cytoskeleton.