Supported gold nanocatalysts have been reported to be active in selective hydrogenation of acetylene. In this work, SiO2 supported Au-Ag bimetallic catalyst is studied in the selective hydrogenation of acetylene in excess ethylene. Au and Ag were reductively deposited on a silica surface functionalized by APTES (3-aminopropyltriethoxysilane). They form Au-Ag alloy nanoparticles of very small size. The catalytic activity of Au-Ag bimetallic system showed better catalytic activity at high temperature than that of monometallic gold catalyst. According to the TEM and XRD results, Ag stabilized the nanoparticles against sintering during high temperature calcinations. Non-thermal O-2 plasma was applied to remove the APTES under mild conditions instead of high temperature calcination. The results showed that the conversion of acetylene was much higher over Au-Ag/SiO2 catalyst pretreated by O-2 plasma than that of pretreated by calcination at 500 degrees C, although the latter catalyst had similar particle size. (C) 2012 Elsevier B.V. All rights reserved.