Abstract: We used LC-MS-MS to investigate the biodegradation capacity of 7 PAEs by activated sludge. The results reveal that first-order kinetics equation can describe the degradation process of PAEs, and the degradation rate constants decrease with the increase of the molecular weight and initial concentration of PAEs. The degradation capacity of activated sludge is enhanced when several kinds of PAEs existed simultaneously. Temperature and pH affect the degradation directly, and the optimal conditions for the biodegradation are 36.7 ℃ and pH 7.6.