In this paper, a dairy wastewater treatment was performed by electro-Fenton process using iron electrode. The experiments were conducted to evaluate the effect of five important parameters including reaction time, current density, pH, H2O2/Fe2+ molar ratio and H2O2/Dairy wastewater (DW) (ml/l) on the performance of the process. The response surface methodology was applied to minimize the number of runs and investigate the optimum operating condition. Five independent variables were carefully considered and optimized in this research. The optimum conditions were reaction time of 90 min, current density of 56 mA/cm(2), pH of 7.52, H2O2/DW volumetric ratio of 0.898 ml/l and H2O2/Fe2+ molar ratio of 3.965 for 93.93% COD removal while the optimum conditions were reaction time of 86 min, current density of 55.1 mA/cm(2), pH of 7.48, H2O2/DW volumetric ratio of 0.907 ml/l and H2O2/Fe2+ molar ratio of 3.987 for 97.32% color removal. (C) 2016 Elsevier B.V. All rights reserved.