We report the catalytic activity of Pt/SiO2 nanocatalysts synthesized via the ultrasonic spray pyrolysis (USP) process under CO oxidation. We found that the average particle size of the dispersed platinum nanoparticles can be controlled by changing the concentration of the Pt precursor and the calcination conditions. The amount of loaded platinum on the SiO2 powder increased as the precursor concentration increased, while the specific surface area of the Pt/SiO2 samples decreased. As the calcination temperature and time increased, the size of the platinum particles on the SiO2 increased. As for catalytic reactivity, high loading of Pt/SiO2 showed a higher conversion of CO. The turnover rate of the Pt/SiO2 catalysts increased after calcination at 600 degrees C, then decreased after calcination at 750 degrees C, mainly due to agglomeration at the high temperature and partly because of severe oxidation. The catalytic activity of the Pt/SiO2 nanocatalysts synthesized using LISP exhibited higher catalytic activity compared with Pt/SiO2 synthesized via wet chemical synthesis or wetness impregnation. It is attributed to better dispersion of the nanoparticles on the SiO2 as well as the removal of hydrocarbon impurities during calcination. This work demonstrated the successful use of the spray pyrolysis process for synthesis of oxide-supported metal catalysts with high thermal stability and activity. (C) 2014 Elsevier B.V. All rights reserved.