A series of CeO_2–ZrO_2–WO_3(CZW)catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction(SCR)of NO with NH_3 over a wide temperature of 150–550°C.The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H_2O.The fresh catalyst showed above 90% NO_x conversion at 201–459°C,which is applicable to diesel exhaust NO_x purification(200–440°C).The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures(below 300°C),while the activity was notably enhanced at high temperature(above 450°C).The aged CZW catalyst(hydrothermal aging at 700°C for 8 hr)showed almost 80% NO_x conversion at 229–550°C,while the V_2O_5–WO_3/TiO_2 catalyst presented above 80% NO_x conversion at 308–370°C.The effect of structural changes,acidity,and redox properties of CZW on the SCR activity was investigated.The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO_2–ZrO_2 solid solution,amorphous WO_3 phase and optimal acidity.In addition,the formation of WO_3 clusters increased in size as the hydrothermal aging temperature increased,resulting in the collapse of structure,which could further affect the acidity and redox properties. A series of CeO_2-ZrO_2-WO_3 (CZW) catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction (SCR) of NO with NH_3 over a wide temperature of 150-550 ° C. The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H_2O. The fresh catalyst showed above 90% NO_x conversion at 201-459 ° C, which is applicable to diesel exhaust NO_x purification (200-440 ° C). The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures (below 300 ° C), while the activity was not possibly enhanced at high temperature (above 450 ° C). aged CZW catalyst (hydrothermal aging at 700 ° C for 8 hr) showed almost 80% NO_x conversion at 229-550 ° C, while the V_2O_5-WO_3 / TiO_2 catalyst presented above 80% NO_x conversion at 308-370 ° C. The effect of structural changes, acidity, and redox properties of CZW on the SCR activity was investigated. The results indica ted that the excellent hydrothermal stability of CZW was mainly due to the CeO 2 -ZrO 2 solid solution, amorphous WO 3 phase and optimal acidity. In addition, the formation of WO_3 clusters increased in size as the hydrothermal aging temperature increased, resulting in the collapse of structure , which could further affect the acidity and redox properties.