CoOx/TiO2 catalysts synthesized by sol-gel method were investigated for the oxidation of NO to NO2 in excess oxygen. NO oxidation efficiency increased sharply as oxygen concentration increased, while NO concentration showed a negative effect. Under the conditions of 30,000 h(-1) GHSV, 600 ppm NO, 4% O-2, 9% CoOx/TiO2 (450) had the highest NO oxidation efficiency and reached the equilibrium at 300 degrees C with a conversion of 79.8%. The XPS results determined that Co3O4 was the main active phase in 9% CoOx/TiO2 (450) prepared by sol-gel method.