The treatment of simulated wastewater containing Acid Scarlet BS was tested with a two-step process that the pretreatment of Fe(II)-mediated decolorization was followed by the electrochemical oxidation with a three-phase three-dimensional electrodes. The experimental results showed that the decolorization mechanism was reductive destruction for the azo group of the dye molecular rather than flocculation or absorption and that the three-phase three-dimensional electrode can effectively reduce COD in the decolorized wastewater simultaneously by several mechanisms such as absorption, air-oxidation, anodic oxidation, cathodic electrogenerated H2O2 and so on. It was also observed that COD for the decolorized wastewater was easier removed as compared with the original dye wastewater, implying that the first and second stage act synergistically to destroy the organic pollutants.