Abstract: In an acetate buffer medium of pH 4.7,the oxidation of Evans blue by H2O2 was catalyzed by trace amount of Fe(Ⅲ),leading to enhancement of decoloration of evans blue.Under the optimum condition,linear relationship between the magnitude of decrease in absorbance (ΔA) measured at 622.0 nm and the concentration of Fe(Ⅲ) was found in the range of 0.1 to 20.0 μg·L-1.Detection limit (3s/b) of the method found was 1.3×10-7g·L-1.Samples of milk powder,well water and tap water were analyzed by the proposed method for their iron contents,the results obtained were in consistency with those obtained by AAS,with values of RSD′s (n=6) less than 2.5%.Recovery of the method was tested giving values of recovery in the range of 99%-102%.Apparent activation energy and constant of reaction rate of the catalytic reaction system were determined and the values are 34.56 kJ·mol-1 and 2.75×10-2s-1 respectively.