OBJECTIVE To investigate the anti-tumor function of ginsenoside Rg3 on hepatocellular carcinoma (HCC) in vitro and in vivo, and its mechanism. METHODS Hep1-6 and HepG2 cells were treated by Rg3 in different concentrations (0, 50, 100 and 200 μg/mL) in vitro. After incubation for 0, 6, 12, 24 and 48 h, cell viability was measured by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling. Caspase-3 activity was measured by chromophore p-nitroanilide and flow cytometry. Bcl-2 family proteins were ascertained by Western-blotting. Mitochondria membrane potential was detected by 5, 5', 6' 6' - tetrachloro-1, 1', 3, 3' - tetraethylbenzimidazolylcarbocyanine iodide. Forty liver tumor-bearing C57Bl6 mice were divided randomly into 4 groups for intra-tumor injection of saline, ginsenoside Rg3, cyclophosphamide (CTX) and ginsenoside Rg3 + CTX combination. RESULTS The survival time was followed up to 102 d. The mice in the Rg3 + CTX group showed significant increased survival time compared with those in the control group (P < 0.05). Rg3 could inhibit HCC cell proliferation and induce cell apoptosis in vitro in the concentration and time dependent manner. It also induced mitochondria membrane potential to decrease. Caspase-3 activation can be blocked by the inhibitor z-DEVD-FMK. Bax was up-regulated while Bcl-2 and Bcl-XL were down-regulated after Rg3 treatment. CONCLUSIONS Our data suggested that Rg3 alone or combined with CTX inhibited tumor growth in vivo and prolonged mouse survival time by inducing HCC cell apoptosis via intrinsic pathway by expression alterations of Bcl-2 family proteins.