Abstract: A complex enzyme production strain for chitosan biodegradation was isolated from soil based on the method of using chitosan as the sole carbon source and solid fermentation medium as the second screening medium. And the strain is identified as Aspergillus based on its morphology observation. Chitosanase, cellulase and α-amylase were the main components in complex enzymes, and the activity of these enzymes was 2.206, 0.790, 3.299U/mL, respectively. Moreover, the optimal conditions for chitosan biodegradation was 50℃, pH5.6 and the optimal operate time was 4h based on the measuring of reducing sugar produced from chitosan hydrolyzation. Finally, the potential use of this complex enzyme in preparation of chitooligosaccharides was confirmed by organic solvent precipitation method.