Abstract: To solve the problems of water environment pollution caused by diuron, the degradation effect of diuron by dielectric barrier discharge plasma was studied. The wire-cylinder dielectric barrier discharge reactor was adopted for aqueous diuron removal. The effect of different parameters on the diuron degradation, and the degradation mechanism of diuron were detected. The results showed that the input power and airflow were the important parameters for the degradation of diuron. When discharge power was 50 W and the air flow was 140 L/h, the degradation rate of diuron was 95.7% with 6 min discharge time. The concentration of O₃ and H₂O₂ increased with increasing discharge time. The pH decreased from 6.3 to 3.4, and the concentrations of TOC decreased from 14.2 mg/L to 11.9 mg/L. The concentrations of Cl^-and NO₃^- were determined by ion chromatograph, which increased significantly with increasing discharge time during diuron degradation process. The change of acute toxic was representative by the inhibition rate of Photobacterium during diuron degradation process. After 6 mininues, the inhibition rate of Photobacterium was 90.5%, and the increasing toxicity trend was observed for the treated diuron solution. Diuron degradation byproducts were confirmed by liquid chromatography-time-of-flight mass spectrometry, the degradation intermediates of diuron were formed mainly by dechlorination hydroxyl, alkyl oxidation reaction and dechlorination hydroxyl combined with alkyl oxidation reaction.