An iron-doped (using limonite as the source of iron) cathode with PEI/MWCNT (polyethylenimine/ Multi- walled carbon nanotube) modified carbon felt outer layers was prepared for Electro-Fenton systems. PEI/MWCNT multi-layers could significantly increase the production of H₂O₂. The highest H₂O₂ accumulation was achieved up to 66.5 ± 2.4 mg/L at -0.95 V, neutral pH and 200 mL/min of aeration rate, which increased about 56.8% than the carbon felt at the same condition. The PEI/MWCNT multi-layers were stable enough that there was no obvious decrease in H₂O₂ accumulation after 20 recycles. This study tested the performance of the prepared cathode in treating the simulated dyeing wastewater. The results were as follows: Orange II with initial concentration of 20 mg/L at neutral pH (pH₀=6-7) was discolored completely after 60 min electrolysis process, and the decolorizing efficiency was up to 96.8%. In addition, the prepared cathode was stable enough and could be reused without catalytic activity decrease. This study also tested the performance of the prepared cathode in treating the actual dyeing wastewater. The chroma, COD and ammonia-nitrogen removal efficiency after 120 min electrolysis process were 91.7%, 69.4%, and 56.2% respectively.