Abstract: Objective To establish the HepG cell line with stably transfected hepatitis B virus X gene and to study its effects on the p53-p21 pathway. Methods Lipofectamine was used to transfect the eukaryotic expression vector pcDNA3.1-HBx into human hepatocellular carcinoma cell line HepG2. G418 was used to select the cell clones for stable expression of the HBx protein of HBV. Cell growth curve and clone plate experiment were used to analyse the malignant phenotype and the growth of hepatocellular carcinoma cells. Flow cytometry was used to assay the apoptosis rate and cell cycle. p53 protein expression levels were detected by Western blot and p21mRNA levels were detected by RT-PCR. Results pcDNA3.1-HBx gene HepG2 cell line was successfully established. The cell growth and clone plate assay revealed that these cells had a relatively increased malignant phenotype. The results of fl ow cytometry also manifested that apoptosis rate of these transfected cells were higher than that of HepG2 cells. The cell number of G₁/G₀ cycle phase decreased and the cell number of G₂ cycle phase increased, while the expression of p53 protein increased and p21 mRNA decreased in those cells. Conclusion The HBx protein could promote the growth of hepatocellular carcinoma cells. The cell line stably tansfected by HBx gene could enhance its malignancy through p53-p21 pathway.