Synthesis of supported Ni catalysts with a core/shell structure at the multibubble sonoluminescence (MBSL) condition and their catalytic tests for methane decomposition by partial oxidation were performed in this study. The catalysts prepared were analyzed by XRD, TEM and XPS. Without doping the third components, the supported catalyst of core/shell structure made with 10% Ni loading on Al(2)O(3) yields 96% conversion efficiency of methane at reaction temperature of 800 degrees C and shows excellent thermal stability for the first 40 h. It turns out that coexistence of NiO and NiOx species on the surface of the catalysts play a very important role in the partial oxidation of methane. In addition, the uniform layer of Ni particles on the surface of support material hindered coke formation and sintering process, which enhances thermal stability for the catalysts. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.