OBJECTIVE：To study the effects of Akt inhibitor MK-2206 on the proliferation and apoptosis of lung adenocarcinoma A549 cells. METHODS：The optical density of A549 cells was detected by MTT assay after treated with 0（blank control），0.5， 1，2.5，5，10，20 and 30 μmol/L MK-2206 for 24 h；after pretreatment with 0（blank control），5，10 and 20 μmol/L MK-2206 for 24 h，morphological changes of A549 cells were observed with inverted microscope. Cell cycle and apoptosis rate were analyzed by flow cytometry. Western blot was used to detect the expression of cell cycle-related proteins Cyclin D1，p21 and p27 and apoptosis- related protein PARP（cf-PARP），cf-caspase-3，Bcl-2 and Bax. RESULTS：Compared with blank control，the optical density of A549 cells decreased，cells shrank and presented vesicular state after treatment of MK-2206；A549 cells arrested in G0/G1 stage， the protein expression of p21 and p27 strengthened while that of Cyclin D1 decreased；the apoptotic rate of cells increased，the expression of cf-PARP，cf-caspase-3 and Bax in cells increased while that of Bcl-2 decreased. All reponse were in concentration-dependant manner （P＜0.05 or P＜0.01）. CONCLUSIONS：MK-2206 can inhibit the proliferation of A549 cells，and induce the apoptosis of A549 cells by adjusting the expression of activating caspase-3，down-regulating Bcl-2 and up-regulating Bax.