Abstract: To utilize sugarcane bagasse and prepare cellulose acetate of high degree of substitution, sugarcane bagasse (SCB) was mechanically activated by a stirring-type ball mill. Using acetic anhydride as esterification agent and concentrated sulfuric as catalyst, cellulose acetate (CA) was synthesized from sugarcane bagasse with different activation times. The effects of mechanical activation time, reaction time, reaction temperature, amount of catalyst and solid-liquid ratio on esterification of sugarcane bagasse were investigated respectively by using degree of substitution (DS) of cellulose acetate as evaluating parameter. The best conditions of preparation technique were confirmed by anorthogonal test. The results indicated that mechanical activation considerably enhanced the acetylation of sugarcane bagasse. Mechanical activated sugarcane bagasse was easier acetylation than the original sugarcane bagasse. Due to mechanical activation broken the sealing of cellulose by lignin, destroyed the crystalline structure, decreased the degree of crystallinity of cellulose, which made esterification reagent more easily penetrate into the sugarcane bagasse internal. It could increase reactivity and decrease the dependence of reaction time, reaction temperature and amount of catalyst. The degree of substitution of cellulose acetate was 2.81 by acetylation of mechanical activated sugarcane bagasse for 1.0 h and reaction in the conditions of liquid – solid ratio12 mL/g, mass fraction of catalyst 4%, reaction temperature 60℃ and reaction time 3.0 h. The structure of cellulose acetate from sugarcane bagasse were characterized by using infrared spectroscopy (IR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results would provide a base and data for the preparation of cellulose acetate of high degree of substitution.