In this study, the reaction mechanisms and kinetic of UV/O 3 digestion processes were explored with ammonium chloride and urea as the target pollutants, focused on the ozone direct oxidation and hydroxyl radical oxidation parts.Under the conditions of dual environmental digestion method, two kinds of kinetic models were proposed by competitive kinetic method with R ct based on the different scale of rate constants of hydroxyl radical oxidation. Subsequently, the second-order rate constants of ammonia (pH 11) and urea (pH 2) was determined to be 4.613 ± 0.094 and 0.378 ± 0.006 M -1 s -1 by ozone direct oxidation, and (6.154 ± 0.971) × 10 7 and (2.257 ± 0.513) × 10 6 M -1 s -1 by hydroxyl radical oxidation, respectively. Compared with contribution level of two parts to the digestion process, it was shown that in the digestion of ammonia, ozone and •OH radical contribute equally (58.86%, 41.14%). In contrast, in the case of urea, ozone (86.10%) contributes more than •OH radical.