In order to extend the application of cornstarch, cornstarch was used as the raw material and sodium dodecylbenzene sulfonate was used as the esterification agent to prepare starch dodecylbenzene sulfonate. Its structure was characterized by using IR. Meanwhile, the degree of substitution (DS), viscosity and thermal stability of starch dodecylbenzene sulfonate was evaluated by different mole ratios between cornstarch and sodium dodecylbenzene sulfonate, reaction time and pH. Results indicated that sodium dodecylbenzene sulfonate-cornstarch ratio of 0.06, reaction time of 4 h and reaction pH of 14 resulted in the appropriate DS, the highest viscosity and thermal stability of prepared starch dodecylbenzene sulfonate.