Synthesis gas was produced by the partial oxidation of methane with using supported 10 ~ 15 wt% Ni catalysts. The highest catalytic activity was obtained with MgO support when Ni loading was 13 wt%. With the 13 wt% Ni/MgO catalyst, methane conversion was 80%, and CO and H₂ selectivities were 93% and 94%, respectively. The activity of the catalyst remained nearly constant after 180 h of the reaction. To investigate the arguing reaction mechanism of this reaction, the temperature of the catalyst bed at top and bottom of the bed were measured with pulsed of the reactants (CH₄:O₂ = 2:1); the changes in the moles of the reactants and products were tested with time; and O₂-TPD experiment was carried out. As a result, it is found that the reaction takes place by a two-step reaction - first, total oxidation of methane to CO₂ and H₂O takes place, and then the produced CO₂ and H₂O are further reacted with CH₄ to tive synthesis gas.