A series of potassium promoted Ru/meso-macroporous SiO2 catalysts were prepared and used for the preferential oxidation of CO (CO-PROX) in H-2-rich gases. The catalysts were characterized by using techniques of TEM, SEM TPR, XPS, and N-2 adsorption/desorption. The catalytic activity of Ru/meso-macroporous SiO2 was markedly improved by the introduction of potassium. The catalyst of K-5 wt.% Ru/meso-macroporous SiO2 with molar ratio of K:Ru = 5:7 exhibited relatively high activity and selectivity for CO-PROX. Nanoparticles of ruthenium species can be highly dispersed on the meso-macroporous SiO2 support by the simple impregnation method. The addition of potassium weakened the interaction between metallic Ru and the silica support. Lowering the reduction temperature of ruthenium ions could keep ruthenium in the state of metallic Ru, and it was proposed that potassium acted as an electron donating agent. The electron donating effect of potassium improved the low temperature activity for CO oxidation and increased the selectivity of O-2 for CO oxidation, thus K-modified Ru/meso-macroporous SiO2 catalyst showed obviously a wide temperature window for CO elimination from H-2-rich gases, meanwhile the related mechanism was discussed. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.