Abstract:Polysaccharide is considered to be a kind of macromolecule substance with a variety of biological activities.It is considered as an ideal raw materials for food and medicine due to its safety and few side effects.Chemical modification can improve structure characteristics，and biological activities of polysaccharides.The biological activity of modified polysaccharides is different with different structure.Therefore，this paper summarized the research progress of polysaccharide chemical modification，included methods，structural characteristics and structure-activity relationship，prospected the application of this method for polysaccharides，in order to provided reference for the development of new functional foods and drugs.