The degradation of methyl orange (MO) was explored in the presence of redox mediator via electrochemical reaction in an undivided cell. The results revealed that the color of the solution changed from orange to colorless during electrolysis. The main factors affecting the degradation rate of methyl orange were the concentration of methyl orange, the current density, and the kind of electrolyte, the pH, and the electrode materials. A minor factor was the concentration of NaBr. In this system, the maximum value of the degradation rate of MO was 30 mg coul(-1) under optimum operating conditions, i. e., the best operating conditions were 20 ppm. methyl orange, 1.25 mA cm(-2), 0.025 M NaBr, and pH 6.8, using graphite as the anode and cathode.