Abstract: Taking Fenghua taro starch as raw materials, and octenyl succinic anhydride (OSA) as esterifying agent, octenyl succinate taro starch ester (OSTS) was prepared in this work. The degree of substitution (DS) of starch esters was determined by high performance liquid chromatography, and the esterification conditions were optimized by single-factor experiments and response surface methodology using the degree of substitution as the response value, and then the physicochemical properties of OSTS, such as surface hydrophobicity, X-ray diffraction and morphology were measured. The results showed that the optimal process was: Starch concentration 40% (w/v), pH8.5, reaction time 2.5 h, reaction temperature 41℃, and the degree of substitution of OSTS obtained under these conditions was 0.02069. After esterification, the contact angle of taro starch changed from 86.2° to 120.9°, which meant the hydrophobicity of starch surface increased. Starch crystal shape was not affected after esterification, indicating that the esterification reaction between OSA and taro starch preferred to the surface of starch particles. The relative crystallinity decreased from 19.04% to 15.20%. This study would provide a theoretical basis for the effective reaction between OSA and small granular starch.