The decolorization of Evans Blue (EB), a diazo dye, by Fenton process under anaerobic conditions has been investigated using cyclic voltammetry technique. Effects of solution pH, concentrations of H2O2, Fe2+ and EB on the decolorization of EB have also been studied. About 98.9% decolorization was found under the optimal conditions [EB] : [Fe2+] : [H2O2] = 1 : 1.9 : 4.7 and [H2O2]/[Fe2+] = 2.5 at pH 2 in 403 seconds. The kinetic data at pH 2 revealed that Behnajady-Modirshahla-Ghanbery (BMG) model was more favorable to describe the decolorization of EB than the zero-, first- and second- order kinetic models. Our experimental results will provide a fundamental knowledge for the more effective treatment of EB in a short time by Fenton's reagent.