The performance of UV/H2O2, UV/O3 and UV/H2O2/O3 oxidation systems for treating spent caustic froman ethylene plant was investigated. In UV/H2O2 system, with the increase of H2O2 dosage, removal efficiencies ofCOD and the ratio of biochemical oxygen demand(BOD) to chemical oxygen demand(COD) of the effluent wereincreased and a better performance was obtained than the H2O2 system alone. In UV/H2O2 system, removalefficiency of COD reach 68% under the optimum condition, and BOD/COD ratio was significantly increased from0.22 to 0.52. In UV/O3 system, with the increase of O3 dosage, removal efficiency of COD and BOD/COD ratiowere increased, and a better performance was obtained than the O3 system alone. Under the optimum condition,removal efficiency of COD was 54%, and BOD/COD ratio was significantly increased from 0.22 to 0.48. In UV/H2O2/O3 system, COD removal efficiency was found to be 22.0% higher than UV/O3 system.