Abstract: A new cavitation method of venturi tube was applied to degrade chitosan in this paper. The effect of chitosan concentration,p H,temperature,inlet pressure and cavitation time on the degradation of chitosan by venturi tube were studied,with the intrinsic viscosity reduction rate of chitosan as a measure indicator. The structures of initial chitosan and the degradation product were characterized by Fourier-transform infrared spectroscopy and X-ray diffraction. The results showed that under the condition of solution concentration at3 g/L,the optimum degradation condition for p H4.4,temperature 60 ℃,inlet pressure 0.4 MPa,cavitation time of 120 min,the intrinsic viscosity reduction rate reached 49%. It illustrated that hydrodynamic cavitation based on the venturi tube could degrade chitosan effectively.