Abstract: In order to prepare chitooligosaccharides with high degree of polymerization(DP),this study explored the feasibility of membrane-coupled enzymatic hydrolysis in the preparation of high DP chitooligosaccharide. And chitooligosaccharides were prepared by batch enzymatic hydrolysis method and membrane-coupled enzymatic hydrolysis process. Results proved that membrane-coupled enzymatic hydrolysis process was more efficient for the preparation of chitooligosaccharides with high DP. The total yield of DP 4~8 chitooligosaccharides was 78.1%,and the contents of DP 4~8 chitooligosaccharides in the final product were 16.5%,35.8%,18.9%,7.81% and 5.12%,respectively. Moreover,flat sheet membrane system was replaced by spiral-wound membrane system,and the irreversible membrane fouling was negligible(R_if=1.56×10⁶ m^-1)because of the cross flow filtration pattern,which increased the applicative concentration of chitosan substrate(30 g/L). And the system could continuously produce high DP chitooligosaccharides for long time. In conclusion,this study would provide an efficient method to produce high DP chitooligosaccharides,which would be the basis of the application and functional research of chitooligosaccharides.