Abstract: The mechanical degradation process of chitosan by high-speed shear technology was studied in this paper. The effects of shear time, rotational speed, temperature, initial concentration of chitosan solution, molecular weight of chitosan and pH of solution on the degradation of chitosan were investigated. The dynamic viscosity reduction rate of chitosan was used to reflect the degradation degree of chitosan. The structure and molecular weight distribution of chitosan before and after degradation were analyzed by fourier transform-infrared spectroscopy and gel permeation chromatography, respectively. The results showed that pure mechanical action could promote the degradation of chitosan. When the initial solution concentration was 3 g/L, molecular weight of chitosan was 100×10⁴, pH was 4.6, temperature was 40 ℃, shear time was 40 min, and rotational speed was 20000 r/min, the degradation effect was the most obvious, and the dynamic viscosity reduction rate was 20.27%.It was also found that the viscosity had a certain influence on the mechanical degradation process of chitosan. When the viscosity of chitosan solution was 4.0 mPa·s, the viscosity of chitosan decreased most. This paper provides a theoretical basis for further exploring the degradation mechanism of chitosan.