Abstract: In order to break up the azo bond and naphthalene ring in the Acid Orange Ⅱ molecule,and to improve the biodegradability of Orange Ⅱ wastewater,300 mg/L Orange Ⅱ simulated wastewater was treated by Electro-Fenton oxidation,and the effects of different current densities on the treatment efficiency were studied.The results showed that under different current density conditions,the CODCr mass concentration of the simulated wastewater rapidly decreased from 377.8 mg/L to 276.9 mg/L,with power consumption of 300 C(10.0 mA/cm2),810 C(7.5 mA/cm2),2190 C(5.0 mA/cm2),and 1710 C(2.5 mA/cm2),respectively.It could be seen that under the high current density conditions,the Acid Orange Ⅱ bonds could be broken up rapidly and efficiently with the lowest power consumption by the Electro-Fenton reactor.The UV-visible spectrum of the effluent showed that under the high current density(7.5 mA/cm2) condition,the azo bond and naphthalene ring of Acid Orange Ⅱ could be completely broken down in 10 min,and the biodegradability of the wastewater was efficiently improved.