Abstract: Chitooligosaccharide could be obtained by chemical and enzymatic hydrolysis of chitosan. It had good physical properties( low molecular weight,good solubility,high absorption and biocompatibility,etc.),and various physiological activities( immune function regulation,antitumous and antioxidative activities effects,etc.),which makes its promising use in the fields of food,medicine,etc.In this review,chitooligosaccharide preparation and its physiological activity were highly summarized,and the prospect of chitooligosaccharide was proposed.