A series of Au/CuOx-TiO2 catalysts with various Cu/Ti atomic ratios were prepared by deposition-precipitation method. The catalysts were characterized by inductively coupled plasma-mass spectrometry, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The preferential oxidation of CO in H2 stream (PROX) on these catalysts was carried out in a fixed bed microreactor with a gas mixture (CO:O2:H 2:He ) 1.33:1.33:65.33:32.01 by volume ratios) was fed with a space velocity of 30000 mL/(g • h). Au/CuOx-TiO2 with various Cu/Ti atomic ratios showed similar gold particle size (2.3-2.5 nm). The gold in the starting material was almost totally loaded on the CuO x-TiO2 support at pH ) 7. Au/CuOx-TiO 2 catalysts with gold content of 1 wt % and calcined at 180 °C had superior catalytic activity and selectivity for CO oxidation at temperature of 80 °C. Au/CuOx-TiO2 (Cu/Ti ) 4.8/95.2) had a CO conversion of 100% at 80 °C, and CO selectivity reaches 68%. Gold particles were well dispersed and stable on the support. Even after PROX reaction at 80 °C for a long time, most of the particles still maintained at ∼2.4 nm. The CO conversion slightly decreased from 100% to 95%, and CO selectivity was nearly the same. Au/CuOx-TiO2 is a highly effective and thermally stable catalyst for PROX reaction compared with Au/TiO2 catalyst. © 2010 American Chemical Society.