To construct a novel gene delivery vector using polyethylenimine (PEI) as backbone modified with the peptide CP9 containing Arginine-Glycine-Aspartic acid (RGD) sequence and to verify its physicochemical characters and the gene delivery function. The chemical linker [N-Succinimidyl-3- (2-pyridyldithio) ] propionate (SPDP) was employed to bind CP9 onto PEI to form a novel gene delivery vector CP9-PEI. The (1)H-NMR and FT-IR were used to verify the linkage of CP9. The plasmid DNA condensing ability of CP9-PEI,the shape and the particle size of the polyplexes formed with CP9-PEI-plasmid DNA were demonstrated by gel retardation assay, electron microscope observation and particle size assay,respectively. The enhanced transfection efficiency and the integrin targeting capacity were detected by the transfection experiments in HepG2 cells and free RGD peptide inhibition test. CP9 was linked onto PEI successfully. The new synthesized vector CP9-PEI could efficiently condense plasmid DNA at N/P ratio of 4 and when N/P ratio was equal to 10, the shape of polyplexes formed with CP9-PEI-plasmid DNA was round or round-alike with particle size of about 200 nm. The transfection efficiency of CP9-PEI was nearly 2 times of PEI in HepG2 cells and the free RGD peptide had the inhibition effect on the efficiency of CP9-PEI. The modification of CP9 on PEI can improve the transfection efficiency of PEI and has the integrin targeting ability.