Abstract：Bagasse xylan acetates was synthesized by using bagasse xylan as raw materials, acetic anhydride as esterifying agent, p-toluenesulfonic acid(PTSA) as activation catalyst and acetic acid as the solvent. The influence of reaction conditions on the degree of substitution of bagasse xylan acetates was investigated. The degree of substitution of the product was 0.20 under the donditions of m(xylan)∶m(acetic anhydride)=4∶5, m(xylan)∶m(PTSA)=4∶0.2, m(xylan)∶m(acetic acid)=4∶10.49, reaction temperature 70℃, reaction time 4h. The structure was characterizated by FTIR，XRD and SEM. Gelatinization Characteristics and thermal viscosity of Bagasse xylan acetates was separately determined, which indicated that the gelatinization temperature of Bagasse xylan acetates was lower and the stability characteristics of thermal viscosity was significantly improved.