Esterified starch samples with low,moderate and high levels of substitution degrees (DS) were prepared in dry-state with acetic anhydride by using NaOH as catalyst.FTIR and XRD were applied to detect the changes of starch structure after the modification.The results showed that the associated hydroxyl groups in starch declined sharply,but the carbonyl group and ester group grew gradually with the increase of DS. The crystallinity in starch granule was decreased along with the modification. Changes of carboxyl group content during the modification demonstrated that the esterification of starch fitted the characteristic of second-order reaction kinetics.The reaction activation energy was 36.16 kJ/mol.
