2-Phenyl-4-quinoIones series compounds have exhibited the influences of growth inhibitory on several human cancer cell lines. In this study, we investigated the effects of 2-(3-(methylamino)phenyl) -6-(pyrrolidin-l-yl)quinolin-4-one (Smh-3) on viability, cell cycle and apoptotic cell death occurred in different leukemia cell lines (HL-60, U937 and K562) in a dose- and time-dependent manner, but it did not obviously impair the viability of normal human umbilical vein endothelial cells (HUVEC) in vitro. The approximate IC50 was 103.26�4.59 nM for a 48-h treatment in HL-60 cells. Cell cycle analysis showed that 100 nM Smh-3 induced significant G2/M arrest in examined cells. Within 0, 12, 24 and 48 h treatment, Smh-3 inhibited the CDK1 activity and decreased protein levels of CDK1, cyclin A, cyclin B. Smh-3-induced chromatin condensation and DNA fragmentation were determined by DAPI and TUNEL staining. Cell apoptosis significantly reduced after proretrea:atmenent with a pan-caspase inhibitor (Z-VAD-fmk) and results indicated that Smh-3 induced apoptosis was mainly mediated by activation of caspase cascade in HL-60 cells. Results from colorimetric assays and Western blot analysis indicated that activities of caspase-9, caspase-7 and caspase-3 were promoted in Smh-3-treated HL-60 cells during cell apoptosis. Smh-3-induced apoptosis in HL-60 cells was accompanied by an apparent increase of ROS production, and protein levels of cytosolic cytochrome c, apoptotic protease activating factor-1 (Apaf-1) and apoptosis-inducing factor (AIF). Strikingly, Smh-3 induced apoptosis in HL-60 cells by simultaneously suppressing protein levels AKT activity, p-AKT, p-mTOR and p-BAD and inducing BAD protein levels. Taken together, we conclude that Smh-3 acted against leukemia cells in vitro via G2/M phase arrest, down-regulation of AKT activity and induction of mitochondria-dependent apoptotic pathways.