Starch-based emulsifiers have a good application prospect in food industry because of their natural and extensive sources,and good compatibility with other food components.A starch-based emulsifier was prepared by oxidation and acetylation of corn starch,and its pasting and emulsifying properties induced by acetyl-carboxy interaction were studied in this paper.Acetylation was restrained by high degree of oxidation,and oxidized starch acetates having 0.26 % of carboxyl content and acetyl/carboxyl ratios between 1.64~3.03 were prepared when the adding ratio of modifying agents(acetic anhydride/sodium hypochlorite) was between 1.33~2.67.Under the above conditions,the modified starch had paste viscosity between 273~295 mPa·s at 6 %(w/v) and showed good emulsifying properties.