Abstract: On the basis of temperature and pH stability of chitosanase,the enzymatic hydrolysis conditions of high concentration solution of chitosan were optimized by adding enzyme during dissolving. The effects of time of adding chitosanase and chitosanase concentration on efficiency of enzymatic hydrolysis of 8% chitosan solution and solution viscosity were studied,and the content of target chitosan oligosaccharides before or after optimization were determined.Results showed that chitosanase can remain stability between 45~55℃, pH4.5~5.5. For 8% chitosan solution, when hydrochloric acid concentration was 0.17 mol/L,2 U/g chitosan chitosanase was added,and when the concentration of hydrochloric acid was 0.48 mol/L,3 U/g chitosan chitosanase was added again.This scheme can effectively reduce the solution viscosity and maintain enzymatic activity. TLC and HPLC analysis results showed that after above optimization,the content of total GlcN2~GlcN6 and pentamer,haxamer increased significantly,reached 42.7,5.5 and 3.9 mg/mL respectively,which improved the production efficiency greatly.