Abstract: Biological fluidized bed was used for the treatment of synthetic butyl acrylate wastewater. The influence of aeration rate was investigated. It was indicated that redox conditions changed significantly in reactor with the decrease of aeration rate. The decrease of (oxidation-reduction potential) ORP and DO had a significant influence on the degradation of acrylic acid and para-toluene sulphonic acid, which were the two main organic pollutants in the wastewater. When ORP was -272~-106 mV and DO was 0.36-0.93 mg/L, the average removal rate of acrylic acid was over 97%. When ORP was below -245 mV, the concentration of degradation intermediate of acrylic acid, acetic acid and propionic acid, increased significantly in effluent. When ORP was -128~-106 mV, concentration of acetic acid was 9.42 mg/L and propionic acid was not detected. When ORP was -272~-245 mV, concentration of acetic acid and propionic acid increased to 65.3 mg/L and 296.0 mg/L, respectively. When ORP was -128~-106 mV and DO was 0.7-0.93 mg/L, average removal rate of para-toluene sulphonic acid was 87%. When ORP was below -179 mV and DO was below 0.53 mg/L, the removal rate of para-toluene sulphonic acid was between 20% and 24%. When ORP was changed from -128~-106 mV to -272~-245 mV, the average removal rate of dissolved organic carbon (DOC) decreased from 89.9% to 46.1%.