Laboratory produced iron hydroxide was tested for its activity in catalytic ozonation of trace nitrobenzene (NB) in water. The catalysis mechanism was deduced from the effect of tert-butanol on the reaction and the difference of catalytic activity between several typical transition metal oxides. Effects of catalyst dose, pH, bicarbonate ion, and times of catalyst reuse on NB removal were also examined. The iron hydroxide showed high catalytic activity on ozonation of NB with removal rate of NB dissolved in distilled water increased by 44.8% at reaction time of 20min. The catalysis follows a hydroxyl radical pathway and is affected by density of hydroxyl groups on the oxide. An optimal catalyst dosage of 100mg/L existed in this experiment. Solution pH near pH of zero charged surface of the oxide favored NB removal and bicarbonate concentration of 2.38mmol/L significantly reduced it. The oxide was used for five times with no significant change of its activity and no dissolution was observed.