A series of Ag-Ru/CeO2 catalysts were prepared by conventional impregnation methods and characterized by XRD, BET, XPS, H-2-TPR, H-2-TPD-MS, and N-2-TPD. The activity test shows that ammonia concentration of the catalyst with 6% Ag is 9.4% at 10 MPa, 10,000 h(-1), 400 degrees C, which is 22% higher than that of Ru/CeO2. Such high catalytic activity was ascribed to three effects: electron donating property of partially reduced CeO2-x to Ru metal, the low workfunction of Ru atoms and the less competitive adsorbed between hydrogen and nitrogen on Ru atoms derived from the synergetic effect between Ag and Ru. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.