Photocatalytic treatment of wastewater containing nitrophenols has been studied. Several kinds of TiO₂ were used for photocatalysts and oxygen and hydrogen peroxide were used for oxidant in this reaction. We have examined the photocatalytic activity of various TiO₂ and simple kinetics. We also examined the effect of reaction conditions, such as reaction temperature, PH, initial concentration of solution, residence time and the effect of oxidant. Anatase-type TiO₂ shows higher activity than rutile-type except for P-25 catalyst. However there is no relationship between catalytic activity and surface area of catalyst. The reaction kinetic shows pseudo first order reaction, The catalytic activity was affected by reaction conditions especially the kind of oxidant. It is thought that OH^- radical plays an important role in the photodegradation of nitrophenol.