Pt/TiO2-C catalyst with TiO2 and carbon black as the mixed support has been synthesized by the microwave-assisted polyol process (MAPP). Effects of anatase TiO2 with different particle sizes and contents on the stability of supported Pt catalysts have been systematically studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammograms (CV), and accelerated potential cycling tests (APCT) have been carried out to present the influence degree. The experimental results indicate that the original electrochemically active specific surface areas (ESA) of the catalysts decrease with the increase of mean particle sizes of TiO2 and TiO2 contents. However, the activity of Pt/TiO2-C-20 is very close to that of Pt/TiO2-C-5 and the stability of Pt/TiO2-C-20 is the best after 1000 cycles APCT, illustrating that the optimized particle size of TiO2 in Pt/TiO2-C catalyst is 20 nm. Furthermore, the stability of the catalysts increase with the increase of TiO2 contents in the mixed support. Taking into account both the activity and stability of various Pt/TiO2-C catalysts, the optimized particle size of TiO2 is 20 nm and the optimal TiO2 content existed in the mixed support is 40%. (C) 2011 Elsevier B.V. All rights reserved.