Abstract: Objective: To investigate the inhibitory action of short hairpin RNA (ShRNA) targeting at the COX- 2 gene expression in HepG2 cells and to determine the effect of ShRNA on the change of cell cycle and cell growth. Methods: A pair of reverse repeated sequence targeting COX- 2 mRNA were contrived and synthesized, with 9 nucleotide sequences between them, and were directionally cloned to the pGenesil- 1, a plasmid vector to construct a recombinant expression plasmid pshRNA-COX- 2, and LipofectamineTM2000, a liposome was used to transfect the hepatocelluar carcinoma cell HepG2. Suppressing effects of the pshRNA- COX- 2 on the COX- 2 mRNA and proteins were detected by the RT- PCR and Western blot methods, respectively. Flow cytometry was conducted to assay the cell cycle and change of the cell growth. Results: Recombinant expression plasmid pshRNA- COX- 2 could inhibit the expression of COX- 2 gene. Compared to the group without transfecting the hepatoma carcinoma cell (HCC) HepG2, the expressions of COX- 2 mRNA and proteins were apparently lower in the group with recombinant expression plasmid pshRNA- COX- 2's transfecting the HCC. The inhibition rates were 69.9% and 50.3% respectively. The cell counts of the G0 and G1 phase were increased from 5.4% to 77.9%, and that of stage S was decreased from 31.1%to16.2 %. The cell growth became signif- icantly slow. Conclusion: Construction of the recombinant expression vector pshRNA- COX- 2 could significantly inhibit the expression of COX- 2 gene, which result in an increase of the cells in the G0 and G1 phase and a decrease of the cells in the S phase, thus suppressing the proliferation of hepato-celluar cells.