The protein kinase B (PKB/Akt) is found over-expression in many kinds of cancer. Here Lipofectamin was used to transfect a consistent active form of PKB (gagPKB) into SMMC 7721 cells to study the ability of the influence of this protein on proliferation and apoptosis of human hepatocellular carcinoma SMMC 7721 cells. The stably over expressing PKB/Akt cell line was identified by Northern blot, Western blot and the assay of PKB activity. Over expressing PKB/Akt promoted cell growth in serum culture and anchorage-indpendent growth in agarose with high efficiency. Alternatively, over-expressing PKB/Akt was sufficient to promote the cells into the S phase of the cell cycle and decreased the expression of the cyclin-dependent kinase inhibitor p27^Kip1. Furthermore, over-expression of PKB/Akt suppressed the apoptosis of cells induced by the detachment of the cells from extracelluar matrix. These results suggest the ability of PKB/Akt to promote proliferation and suppress apoptosis in cancer cells.