In a diaphragm electrolyze system with a Ti/RuO2/IrO2 anode and the Pd/MWNTs gas diffusion cathode, the degradation of 4-chlorophenol was fully studied by the electrochemical reduction and the simultaneous oxidation of the cathode and anode. The results indicated that the optimization electrolyte concentration is 0.08 mol/L. The Cl- removal reached 94.8% after 80 min electrolysis with H2 feeding. After 120 min electrolysis, the removal of 4-chlorophenol in the anodic and cathode compartments were 98.5% and 90.6%, respectively. Additionally, the TOC removal reached 65% and 70% in the anodic and cathodic compartment respectively after 140 min. By the UV scanner analysis of the electrolyte, the 4-chlorophenol and benzoquinone were oxidized by the oxides formed on the cathode, while the benzoquinone was found accumulated in the anodic compartment.