pIRES2-EGFP was employed and a non-target shRNA expressing plasmid was constructed to simulate overexpression and RNAi (RNA interference) experiments. Transfection of pIRES2-EGFP into HEK293A cells by cationic lipids VigoFect demonstrated that transfection efficiency increased in a dose-dependent manner with amount of DNA plasmid used, and optimal transfection time and cell density should be identified to reach a compromise of higher transfection efficiency and lower toxicity. Co-transfection experiments indicated that the two co-transfected plasmids were equivalently delivered into the same cells, and the co-transfection efficiency was rarely affected by cell density and proportion of the two plasmids. However, plasmid-receipted cells seemed indisposed to accept plasmid again during the second transfection, and very low co-transfection efficiency was observed in tandem transfection.