The ClO2 chemical oxidation system and ClO2 catalytic oxidation system are studied in this paper. The results show that pH=6~8, 1000mg ClO2/L wastewater, reacting 60min are the most efficient and economical, when treating Acid Brilliant Scarlet GR dyestuff wastewater, the COD of which is 3500mg/L, by ClO2 chemical oxidation. The COD removal ratio exceeds 50%, and the oxidation index (COD removal amount/ ClO2 used amount) is 2.3. When treating the wastewater by catalytic oxidation which is composed of ClO2 and special catalyst, pH≈2, 800mg ClO2/L wastewater, reacting 45~60min are the most efficient and economical. The COD removal ratio exceeds 80%, and the oxidation index (COD removal amount/ ClO2 used amount) is 3.5. The cost of oxidant removing 1kg COD is ¥3.7. The effect is superior to that of ClO2chemical oxidation apparently. The study indicates that ClO2 catalytic oxidation is an efficient method to treat refractory wastewater and it’ll have a broad prospect.