Objective  To study the feasibility of a eukaryotic vector mediating expression of MDA-7/IL-24 in hepatocellular carcinoma cell line HepG2, the anti-tumor effect of MDA-7/IL-24 in HepG2 cells and possible working mechanism for the tumor-suppressor activity.   Methods   The recombinant plasmid pcDNA3.1(+)-IL-24 and empty plasmid pcDNA3.1(+) were transfected into HepG2 cells by liposome transfection, respectively. Morphological changes of apoptosis were observed under inverted microscope. The proliferation-inhibiting effect of IL-24 in HepG2 cells was observed with Thiazolyl blue assay. Apoptosis ratio and cell-cycle were analyzed by flow cytometry.   Results  The mRNA of IL-24 was detected in HepG2 cells transfected with pcDNA3.1(+)- IL-24 successfully. The typically morphological changes of apoptotis of cells transfected with the target gene were observed obviously. The proliferation-inhibiting rates at 48 h post-transfection (F=27.058, P<0.01), and 72 h post-transfection (F=63.481, P<0.01), and apoptosis indexes (F=326.220，P<0.01) in IL-24 group were significantly higher than those in control groups, with the proportion of cells in the phase of G2/M in IL-24 group being higher, too.   Conclusions   The recombinant eukaryotic vector pcDNA3.1(+) can mediate expression of MDA-7/ IL-24 in HepG2 cells effectively. IL-24 displays growth-inhibiting and apoptosis-inducing activity in HepG2 cells and cell circle arrest in the phase of G2/M  may be the working mechanism of the anti-tumor effect.