RGD peptides were grafted to the carboxyl groups of poly(glutamic acid) to get a targeting shielding carrier (PGA-RGD) for polyethyleneimine (PEI) gene carrier. The experiment results showed that PGA-RGD can effectively shield PEI/DNA complex particles. Gel retardation assay showed that DNA can not be released by PGA-RGD from complexes under experimental conditions for gene transfection. For PGA/PEI/DNA system, its gene transfection efficiency obviously decreased because PGA shielding carrier coating on PEI/DNA complex decreased the surface charges of the complex particles. On the other hand, for PGA-RGD/PEI/DNA shielding system, although its surface charges were decreased by PGA-RGD shielding, its gene transfection efficiency were effectively improved because of the specific binding affinity between RGD and receptors on tumor endothelial cell membranes. MTT assay further presented that PGA-RGD/PEI/DNA has better biocompatibility than PEI/DNA. The improvement method developed in this paper for gene carriers can not only shield the positive charges on complex particles and decrease the non-specific uptake by non-targeting cells, but also introduce targeting functions to gene carrier system. The shielding system for gene complex particles is an effective strategy for promoting in vivo application of polycation gene carriers.