Abstract: Oxidized starch was prepared using corn starch as the raw material and NaClO as the oxidant catalyzed with a complex catalyst 2,2,6,6tetramethylpiperidine1oxyl (TEMPO) and NaBr. Effects of the amount of NaClO, pH of reaction media, reaction temperature and reaction time on the yield and carboxyl group content of oxidized starch were investigated. The suitable oxidation conditions were determined as follows: the amounts of NaClO was 35 % (based on the weight of corn starch) respectively, pH of reaction media was 105, reaction temperature was 0 ℃, reaction time was 25 h. The content of carboxyl group of the oxidized starch obtained on the aforesaid conditions reached 530 %, and the yield of oxidized starch was 888 %. Furthermore, the structure and the application properties of oxidized cornstarch were characterized by IR and SEM. Comparing to raw starch, the paste viscosity of the oxidized starch decreased from 100 mPa·s to 30 mPa·s, and transmittance of paste liquid increased from 4786 % to 9419 %.