Abstract: An electro-Fenton oxidation system using a gas diffusion electrode as the cathode and Ti/SnO₂-Sb₂O₅-IrO₂ as the anode was constructed and used for the degradation of 2,4-dichlorophenol (2,4-DCP). Based on an investigation of the optimal potential for the gas diffusion electrode to generate H₂O₂, the effects of Fe²⁺ and reaction time on the degradation of 2,4-DCP were studied. Moreover, the variations of H₂O₂, Fe²⁺ and Cl^- concentrations during 2,4-DCP degradation were also investigated. The results showed that the degradation of 2,4-DCP was attributed to the co-action of electro-Fenton oxidation and anodic oxidation. Under the cathodic potential of -0.7 V, Fe²⁺ concentration of 0.15 mmol/L and reaction time of 60 minutes, 89.1% of 2,4-DCP was removed. The characteristic absorption peak of 2,4-DCP disappeared completely, and the 2,4-DCP removal rate reached 100% after 120 minutes of treatment. TOC concentration was reduced to 9.15 mg/L, and its removal rate reached 79.4% after 240 minutes of treatment. There was a negative correlation between H₂O₂ and Fe²⁺. After degradation, the chlorine in the molecule of 2,4-DCP existed in the form of Cl^- in the solution.