Abstract: Objective To investigate the influence of small interfering RNA（siRNA） targeting PI3Kp85α on proliferation， migration and invasion of gastric carcinoma cell line AGS. Methods Three siRNA with different sequences （siRNA-1，siRNA-2，siRNA-3） were desinged and transfected into AGS cells. The AGS cells were divided into siRNA groups， universal scrambled negative siRNA groups and blank groups. After transfection， the protein expression of PI3Kp85α was detected by western blotting. MTT assay， wound healing and Transwell assays were performed to detect the effect of PI3Kp85α siRNA on AGS cell proliferation， migration and invasion. Results The expressions of PI3Kp85α protein significantly decreased in the siRNA-2 and siRNA-3 transfected cells. Western blotting analysis showed that cells transfected with siRNA-3 had the strongest inhibition of PI3Kp85α protein， with the inhibition rate being 80％， and siRNA-3 was chosen in the subsequence experiments for gene knockdown. MTT assay and wound healing assay showed that the proliferative and healing ability of PI3Kp85α-knockdown cells was significantly lower than that of the negative control cells since 24 hours after transfection, respectively（P＜0.05）. Transwell assay showed that the cells passing the polycarbonate membranes was significantly less in PI3Kp85αknockdown cells than in the negative control cells （P＜0.05）. Conclusion siRNA down-regulating PI3Kp85α gene in human gastric carcinoma cell line AGS can inhibit cell proliferation，migration and invasion.