Abstract: In order to elucidate the general laws of photocatalytic degradation kinetics, three substituted phenylurea herbicides, including fenuron, isopronuron and linuron, were selected as model compounds to investigate in a system of Xe lamp and TiO₂. The effects of catalyst dosages, initial concentration of substituted phenylurea herbicides, pH value, temperature, reactive oxidative species (ROSs) and electron-captured agents on photocatalytic kinetics were also systematically studied. The results indicated that the degradation kinetics followed a pseudo-first-order by Langmuir-Hinshelwood model, and the rate constants were obtained as 0.0828,0.0687 and 0.0954 min^-1 for fenuron, isopronuron and linuron, respectively. Moreover, the substituted groups on aromatic ring and bridge chain of the urea group significantly affected the degradation rate. The results from ROSs suggested that the contributions of ·OH were 91.6%, 95.5% and 86.8% for fenuron, isopronuron and linuron, which played an important role in the photocatalytic degradation of these three substituted phenylurea herbicides, while photohole and the other ROSs only did minor contributions. Additionally, BrO₃^- and S₂O₈^2- of the electron-captured agents obviously promoted the degradation rates of the three substituted phenylurea herbicides. Based on the results, environmental fate, transfer effect and potential risk of substituted phenylurea herbicides could be properly evaluated in environmental waters.