In the present study, galactosylated chitosan(Gal-CS) was conjugated with methoxy poly(ethylene glycol)(m PEG) as a hydrophilic group. The structure of Gal-CS-m PEG polymer was characterized and the nanoparticles(NPs) were prepared using ironic gelation method. The study was designed to investigate the characteristics and functions of Gal-CS-m PEG NPs. The morphology of Gal-CS-m PEG NPs was observed by SEM and it was a compact and spherical shape. The size of the NPs was approximately 200 nm in diameter under the ideal process parameters. The interaction between Gal-CS-m PEG NPs and p DNA, and the protection of p DNA against DNase I and serum degradation by Gal-CS-m PEG NPs were evaluated. Agarose gel electrophoresis results showed that Gal-CS-m PEG NPs had strong interaction with p DNA at the weight ratio of 12:1, 4:1 and 2:1 and could protect p DNA from DNase I and serum degradation. Gal-CS-m PEG NPs exhibited high loading efficiency and sustainable in vitro release. The blood compatibility studies demonstrated that Gal-CS-m PEG NPs had superior compatibility with erythrocytes in terms of aggregation degree and hemolysis level. Gal-CS-m PEG NPs showed no cytotoxicity on L929 cells, which is a normal mouse connective tissue fibroblast, but showed inhibitory effects on the proliferation of Bel-7402 cells, which is a liver cancer cell line. In conclusion, Gal-CS-m PEG NP is a bio-safe and efficient gene carrier with potential application in gene delivery. The structure of Gal-CS-m PEG polymer was characterized and the nanoparticles (NPs) were prepared The study was designed to investigate the characteristics and functions of Gal-CS-m PEG NPs. The morphology of Gal-CS-m PEG NPs was observed by SEM and it was a compact and spherical shape. The size of The interaction between Gal-CS-m PEG NPs and p DNA, and the protection of p DNA against DNase I and serum degradation by Gal-CS-m PEG NPs was evaluated as . Agarose gel electrophoresis results showed that Gal-CS-m PEG NPs had strong interaction with p DNA at the weight ratio of 12: 1, 4: 1 and 2: 1 and could protect p DNA from DNase I and serum degradation. Gal- CS-m PEG NPs exhibited high loading efficiency and sustainable in vitro release. The blood compat Gal-CS-m PEG NPs showed no cytotoxicity on L929 cells, which is a normal mouse connective tissue fibroblast, but showed inhibitory effects on the proliferation of Bel-7402 cells, which is a liver cancer cell line. In conclusion, Gal-CS-m PEG NP is a bio-safe and efficient gene carrier with potential application in gene delivery.