Abstract: Maleic anhydride esterified corn starch was prepared by dry method with corn starch as raw material and maleic anhydride (MAH) as esterifying agent. The effect of the reaction temperature, reaction time duration and maleic anhydride dosage on substitution degree of esterified starch was studied, and the esterified starch was characterized by Xray diffractometer (XRD) and thermogravimetric analysis (TGA). The results showed that substitution degree of esterified starch increased gradually with the increase of reaction temperature and reaction time duration. When the temperature reached 80℃, or when the reaction time duration was extended to 2.0h, the substitution degree of esterified starch tended to be stable. In the case with excessive starch dosage, the degree of substitution was in linear growth along with the increment of MAH amount. XRD analysis showed that with the increase of MAH amount, esterification reaction caused the degree of crystallinity of starch to decrease gradually. TGA analysis showed that the decreased degree of crystallinity resulted in the reduction of the thermal initiation temperature and the temperature for maximum rate of starch esterification. With the increasing amount of MAH, the reduction effect was more obvious.