The platinum particles-Fe(III) and multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrodes(Pt—Fe(Ⅲ)/MWCNTs/GCE) were prepared by drop coating and electrochemical deposition. The electrocatalytic property of Pt—Fe(Ⅲ)/MWCNTs/GCE on NO₂^- were studied, the experimental conditions were optimized and a differential pulse voltammetric method for determining NO₂^- was established．The oxidation peak current of NO₂^- is proportional to the concentration of NO₂^- over the range of 3.0×10^-7～2.0×10^-3 mol/L with the detection limit of 1.0×10^-7 mol/L (r = 0.999 3). The method was applied to the determination of NO₂^- in food, and the result was satisfactory.