Abstract: To expand the application of high-amylose maize starch in the food industry,the present study was to investigate the optimal process conditions of mildly oxidizing high-amylose maize starch by orthogonal experiment method with sodium hypochlorite as oxidizing agent.The effect of available chlorine amount,pH,the reaction time and the reaction temperature on the aldehyde and carboxyl content of maize starch under mild oxidation conditions was examined.The results showed that the optimum process conditions of mildly oxidizing high-amylose maize starch were as follows:the addition amount of available chlorine of 0.4%,pH of 8,reaction temperature of 55℃ and reaction time of 4 h,under which the aldehyde and carboxyl content were reached to 1.540% and 0.035%,respectively.The starch granule diameter of the optimized high-amylose maize starch with multiple aldehyde was reduced to 8.704 μm,which was decreased by 3.04 μm compared with the original high-amylose maize starch (11.744 μm).The results of Differential Scanning Calorimeter (DSC) test indicated that the gelatinization temperature and enthalpy of the mildly oxidizing high-amylose maize starch were declined;the double helix structure of the starch molecular was depolymerized partly by oxidized;the crystallization field of high-amylose maize starch area was degraded.Thermal Gravimetric Analysis (TGA) tests revealed the maximum decomposition temperature of moderately oxidized high-amylose maize starch was reached to 320.44℃,which implied that the thermal stability of the oxidized starch was increased compared with native starch.