Abstract: Polysaccharides have been paid much attention in many fields on account of their biological activities for instance antioxidant,anti-tumor,immunoregulation and hypoglycemia.The structure of polysaccharides is related to its biological activity,which can be enhanced or produced by chemical modification.In this paper,the modification of carboxymethylation of natural polysaccharides and its effect on biological activity were summarized,in order to provide theoretical reference for the research,development and application of polysaccharides

Key words: polysaccharide, polysaccharide carboxymethylation, biological activity, research progress