Objective To explore the effect of polyethylene glycol-polyethyleneimine (PEG-PEI) serving as a non-viral vector in delivering small interfering RNA (siRNA) into C17.2 neural stem cells (NSCs) in vitro. Methods Complexes of PEG-PEI and siRNA targeting Nogo receptor were prepared, and their characterizations were estimated by measurements of particle size and zeta potential,and the complex abilities of PEG-PEI/siRNA complexes were observed by gel retardation assay. In addition, with liposome complex system (Lipofectamine 2000/siRNA) as positive control, the transfection efficiency of PEI-PEG/siRNA complexes at different N/P ratios (cationic nitrogen/siRNA phosphate molar ratio) was detected by flow cytometry. Results The siRNA molecules were condensed by PEG-PEI to form nanoseale complexes. As the proportion of N/P ratio enhancing, the surface potential of nanoparticles gradually increased and the particle sizes of PEI-PEG/siRNA complexes showed a decreasing trend. Gel retardation electrophoresis suggested that siRNA could be fully composited with PEG-PEI as a result of the coulombic foree between them. Meanwhile, flow cytometry experiments revealed that the transfection efficiency of PEG-PEI mainly depended on N/P ratios of the nanoparticles,and the highest one was obtained at N/P=15 ([78.72±8.18)]％). Conclusion PEG-PEI might be a prospective candidate for siRNA delivery system, which enjoys its value in NSC gene therapy.