We have prepared a series of Au-Pd/SiO2 catalysts by the routine deposition-precipitation method followed by calcination at 200 degrees C in air for 4 h. The structures of these catalysts have been characterized with powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and H-2-temperature-programmed reduction. Their catalytic activity in CO oxidation has also been studied. We found that the preparation procedure leads to the formation of highly dispersed PdO supported on SiO2 in Pd/SiO2, but to the formation of both highly dispersed PdO and AuxPd alloy nanoparticles in Au-Pd/SiO2 catalysts. The fraction of metallic Pd in Pd species increases with the increase of Au:Pd molar ratio in Au-Pd/SiO2 catalysts. We proposed that the alloying of Au and Pd can promote the thermal decomposition of PdO supported on SiO2. Because of the existence of metallic Pd, Au-Pd/SiO2 catalysts are more active in CO oxidation than Pd/SiO2. Au-Pd/SiO2-0.5 exhibits the same activity as Pd/SiO2-H-2 in CO oxidation. Our results provide some novel information on the fabrication of supported AuxPd alloy nanoparticles. (C) 2010 Elsevier B. V. All rights reserved.