Objective To prepare poly(ethylene glycol)-poly(benzyl L-glutamate) amphipathic copolymer nanosphere and evaluate its gene-delivery ability.Methods The amphipathic copolymers were prepared by polymerizing of benzyl L-glutamate N-carboxyanhydride(BLG-NCA) initiated by AT-PEG.The characteristics of the copolymers were measured by IR, 1H-NMR and GPC.The copolymer nanospheres were prepared by the solvent evaporation technique.The microscopic morphology of the nanoparticles were examined by TEM.DNA protection was observed by DNaseⅠdigestion.The GFP gene was used as reporter gene to analyze the gene-delivery ability.Results The copolymers nanospheres are core-shell structures and the diameters are in the range of 60～80 nm.The plasmid DNA can be protected by the PEG-PBLG nanospheres from DNaseⅠ digestion.The GFP expression efficacy was found as well as that of lipofentamine teansfection.Conclusion The PEG-PBLG nanospheres display perfect ability to encapsulate plasmid DNA and can be potentially used as a new vector in gene therapy.