A considerable amount of nitrobenzene, aniline and its derivative that are toxic to organism and difficult to degrade are generated in wastewater from nitrobenzene manufacturing process. After nitrobenzene and aniline wastewater was treated with ClO2 catalytic oxidation process, removal efficiency of COD, nitrobenzene and aniline were up to 90%, 95% and 95% respectively, with concentration of nitrobenzene, aniline and COD under 2.5mg/L, 1.5 mg/L and 100 mg/L respectively.