Comparing to Chitosan, Chitosan-oligosaccharides have several special functions, such as water-soluble, antitumor activity, immunostimulating effects, and antimicrobial activity. The chitosan-oligosaccharide, the molecular weight of which was about 5000, was used as research model. According to the agarose gel electrophoresis and UV spectrophotometer it was proved that electrostatic interaction was playing a very important role in the formation process of chitosan-oligosaccharide/DNA complex. The potential of adsorbing DNA on chitosan-oligosaccharide was analyzed by gel electrophoresis and UV spectrophotometer, and it was indicated that chitosan-oligosaccharide can improve the storage and structure stability of DNA. To check its protection ability to DNA by DNase I digestive experiment, the result showed that chitosan-oligosaccharide could load with plasmid effectively and protect DNA from being digested by DNase I. It was proved that chitosan-oligosacchide was safe and effective for gene delivery and will have a very good future in the field of gene therapy.