Abstract: Panax notogingseng saponins inhibits the growth of several cancer cell lines,but the inhibition of 20(S)-protopanaxadiol saponins (20(S)-PPDS), an aqueous extraction group from stem,leaves,pedicel,and fruit stem of Pannax notoginseng,on the proliferation of lung adenocarcinoma cell line A549 and its possible molecular mechanism is not clear.After treating A549 cells with 20(S)-PPDS,we detected the effects of 20(S)-PPDS on A549 cells by MTT assay,immunohistochemistry,Hoechst33258 staining,and Western blot.The results showed that 20(S)-PPDS inhibited the growth of A549 cells.When treated with 125,250 and 500 μg·mL-1 of 20(S)-PPDS for 72 h,the inhibitory rates of A549 cells were 28.67%,41.97%,73.02% respectively.The 50% inhibition concentration of 20(S)-PPDS were 398.94 and 315.90 μg·mL-1 at 24 and 72 h.20(S)-PPDS induced cell apoptosis through activating Caspase-3,up-regulating Bax,down-regulating Pro-Caspase-3 and Bcl-2 protein expression.Experimental results of this study suggested that 20(S)-PPDS exerts anticancer activity through the growth inhibition and the apoptosis on A549 cells.