Abstract: As a kind of macromolecular substances with biological activities such as anti-oxidation, anti-tumor, anti-bacterial and anti-inflammatory, polysaccharides have attracted extensive interest of researchers in recent years, but some natural polysaccharides have problems such as poor solubility and weak activity. In order to enhance their biological activities, chemical methods can be used to modify the structure of polysaccharides. At present, chemical modification methods are mainly concentrated on sulfation, acetylation,carboxymethylation, phosphorylation, selenidation and so on. In this paper, the specific operation of chemical modification methods and the change of product activity are reviewed, providing reference and reference for the development and utilization of sugar products.