Amaranth azo dye has been degraded by electro-Fenton method using an undivided cell containing the polypyrrole (PPy)/anthraquinonedisulphonate (AQDS) composite film modified graphite cathode and Pt anode. In acidic media, the PPy/AQDS composite film exhibits the characteristic of gas diffusion cathode and is highly efficient for hydrogen peroxide electrogeneration with high generation rate and current efficiency. This new electro-Fenton system can degrade amaranth azo dye efficiently in various acidic solutions. The amaranth decay and total organic carbon (TOC) removal were determined as a function of pH, cathode potential, Fe2+ and doping AQDS concentrations. Total dye decay and 80.3% mineralization were achieved at the optimum conditions (pH 3.0, E-cath = -0.65 V vs. SCE, 2.0 mM Fe2+ concentration). The electrochemical stability and electrocatalytic activity of the composite film after use in electro-Fenton process were also investigated using cyclic voltammetry (CV) and Fourier transfer infrared (FTIR) spectroscopy technologies. (C) 2008 Elsevier Ltd. All rights reserved.