In general, there are three processes for production of synthesis gas; steam reforming, CO2 reforming and partial oxidation of methane or natural gas. In the present work, we refer to tri-reforming of methane to synthesize syngas with desirable H-2/CO ratios by simultaneous oxy-CO2-steam reforming of methane. In this study, we report the results obtained on tri-reforming of methane over the Ni/ZrO2 based catalyst in order to restrain the carbon deposition and to evaluate the catalytic performance. Results of tri-reforming of CH4 by three catalysts (Ni/Ce-ZrO2, Ni/ZrO2 and Haldor Topsoe R67-7H) are showed that the coke on the reactor wall and the surface of catalyst were reduced dramatically. It was found that the weak acidic site, basic site and redox ability of Ce-ZrO2 play an important role in tri-reforming of methane conversion. Carbon deposition depends not only on the nature of support, but also on the oxidant as like steam or oxygen. Therefore, the process optimization by reactant ratios is important to manufacture the synthesis gas from natural gas and carbon dioxide. (C) 2003 Elsevier B.V. All rights reserved.