A system of pulsed high voltage discharge coupling internal electrolysis (PHVDCIE) in water has been developed to remove 4-chlorophenol (4-CP). The hydrogen peroxide formed by discharge was little utilized by 4-CP degradation in the sole discharge system, but most of the hydrogen peroxide could be utilized in the PHVDCIE system to form hydroxyl radicals for the production of Fe2+. The Fe2+ was generated in the cell reaction and was reacted with the hydrogen peroxide through the Fenton's reaction. The formation rate of hydroxyl radical was increased in the PHVDCIE system. It was 5.28 x 10(-7) mol L-1 s(-1) with bubbling oxygen but it was 1.49 x 10(-7) mol L-1 s(-1) in the sole discharge system. With increase in the yields of hydroxyl radical, the 4-CP removal was sped up. The removal efficiency of 4-CP was improved to more than 90% correspondingly by 36 min discharge in the PHVDCIE system. With the promotion of 4-CP degradation, more intermediate products such as formic, acetic and oxalic acid were produced. (C) 2008 Elsevier B.V. All rights reserved.