Abstract: Immunoregulatory activity is one of the most important biological activities of polysaccharides.Polysaccharides can enhance immune activity while offer no side-effects on cells. Appropriate modification on polysaccharide could be good to exert immune function. The common methods for structure modification to improve its immune activity are the chemical method, biological method and physical method. This paper had expounded different methods of polysaccharide modification on the immune activity in recent years and discussed the mechanism of action. It provided reference and basis for further study on the immunologic mechanism and structure-function relationship of polysaccharides.