The modification of ceria (CeO2) on high surface area cobaltic oxide (Co3O4) and the promotion effect of CO oxidation via different pretreatment conditions were studied. The high-valence cobalt oxide was prepared first by precipitation-oxidation in ice bath, followed by reduction at 230 C to get pure and high surface area cobaltic oxide (assigned as 8230, S-BET = 100 m(2) g(-1)). Further, the Ce20/R230 catalyst was prepared by impregnation with cerium nitrate (20% cerium loading). Pretreatment of Ce20/R230 catalyst was divided into two methods: reduction (under 200 and 400 degrees C) and calcination (under 350 and 550 degrees C). The catalysts were characterized by X-ray diffraction (XRD), infrared (IR), and diffuse reflectance spectroscopy (DRS), and temperature-programmed reduction (TPR) and by nitrogen adsorption at -196 degrees C. The results showed that pretreatment under low-temperatures obtained both larger surface area and better activity. The Ce20/R230-H200 catalyst exhibited the highest surface area (S-BET = 109 m(2) g(-1)) and the best catalytic activity in CO oxidation with T-50 (50% conversion) at 88 degrees C among series of catalysts due to the combined effect of cobaltic oxide and ceria. The optimized pretreatment of CeO2/Co3O4 catalysts can clearly enhance the catalytic activity. (c) 2006 Elsevier B.V. All rights reserved.