Abstract: In order to study the preparation process of Sparassis crispa low molecular weight polysaccharide,the effects of sulfuric acid concentration,acid hydrolysis time and sulfuric acid volume on the degree of hydrolysis of polysaccharide were investigated. The hydrolysis degree of Sparassis crispa polysaccharide was used as the response value and fitted by the quadratic mathematical model. The optimum acid hydrolysis process parameters were used,and the molecular weight of polysaccharides before and after acid hydrolysis were determined by multi-angle laser light scattering. The results showed that in the sulfuric acid concentration of 2.5%,the reaction time of 85 min,the liquid to material ratio of 6:1 mL/g,the Sparassis crispa polysaccharide hydrolysis degree was 67.06%±0.77%,which was close to the predicted value,and the model fitting effect was good.Sparassis crispa polysaccharide contained three components,and the weight average molecular weight were 3.32×10⁷,1.79×10⁶ and 3.18×10⁶ Da,respectively. After acid hydrolysis,Sparassis crispa low molecular weight polysaccharide got two groups. The weight average molecular were 3.25×10⁵ and 5.61×10⁵ Da,respectively,and the components were highly uniform before and after acid hydrolysis. This indicated that the preparation of low molecular weight polysaccharides was successful,which would provide a theoretical basis for subsequent separation and purification and biological activity research.