Both transient photolysis and steady-state photo-degradation experiments were performed to gain insight into the kinetics and mechanisms of degradation of p-mitroaniline (p-NA) in aqueous solutions. Monophotonic photo-ionization of p-NA was characterized by 266nm Laser Flash Photolysis (LFP). The quantum yield of eaq(-) was calculated. Radical cations and neutral radicals of p-NA were identified, respectively. The LFP of p-NA with H2O2 in aqueous Solutions was investigated for the first time. For steady-state photodegradation, degradation of p-NA was observed at diverse irradiation conditions under 254 run UV light. Direct photo-degradation of p-NA by 254 nm UV light in aqueous solution was very difficult. Once H2O2 was added into the experimental system, degradation of p-NA was enhanced remarkably. In the absence of O-2, degradation rate increased rapidly along with the irradiation time and reached 80% at 10 min. p-NA could be totally removed after 15 min in UV/H2O2 process. In the presence of O-2 and H2O2, degradation rate increased linearly along with the irradiation time and reached 80% at 7.5 min. p-NA Could be totally removed after 10 min. The mechanisms behind the photo-degradation of p-NA were discussed. (C) 2008 Elsevier B.V. All rights reserved.