As a neotype nonviral vector, (Polyethylenimine, PEI) has been studied in gene transfection experiment. This study was investigated the growth inhibition and radio-sensitizing effect of E1A gene transfected by PEI on human colon carcinoma cell in vitro. The PSV-E1A recombinant plasmid, which was designed for high-level expression of E1A gene in a variety of eukaryotic cell lines, was transfected into SW480 cells by PEI. The transfection was confirmed by RT-PCR and G418 was used to get colon carcinoma cells stably expressed E1A gene. The cell growth curve were investigated to observe the growth inhibition induced by E1A gene. The redistributions of cell cycle were analyzed by flow cytometry. Cells before and after transfection were treated with irradiation, then the changes of radiation-sensitivity were tested by MTT assay after 24 h meanwhile the expression of HER-2 gene in SW480 cells before and after transfection was detected by western-blot. As results, (1) the colon carcinoma cells expressed E1A gene was confirmed by G418. (2)The result of RT-PCR demonstrated that PEI could transfect plasmid psv-E1A and the cells could stably express E1A gene.(3)Flow cytometry revealed that E1A gene transfected into human colon carcinoma cell could induce S stage suppression (,p,<,0.001) and G2/M stage arrest (,p,<,0.001). (4)Compared with the Non-transfected cells, the E1A-transfected cells (SW480-E1A cells) grew slowly observed by MTT assay which was used to get the absorbance of SW480 cell and SW480-E1A cell. (5)The radiation-sensitivity of SW480 cells transfected with E1A gene was up -regulated obviously (,p,<,0.001). (6) The E1A gene obviously down-regulated HER-2 protein expression in colon carcinoma cells. Anyway, PEI can transfect plasmid psv-E1A gene which can significantly inhibit the growth rate of SW480 cell. Moreover, it also obviously enhanced the cell sensitivity to irradiation.