The potential advantages of the UV/H2O2 process treating petrochemical wastewater as the tertiary treatment or the direct pre-treatment were demonstrated. While the high alkalinity of wastewater was not reduced, the UV/H2O2 process as the tertiary treatment could not obtain removal efficiency of wastewater. If the system pH adjusts to 3, this process will polish the effluent of the current biological process to meet the National Effluent Standards of 1998. The results of the direct pre-treatment with the UV/H2O2 process revealed that the recalcitrant compounds presented in raw wastewater would be destroyed to small molecules and might reduce some degree of activity inhibition to bioculture. In the detoxified investigation of spiking aromatic compounds, this process could obtain a good removal efficiency, including a lot of COD removal and the complete detoxification.