Synthesis gas production by the partial oxidation of methane has been investigated using BaO, CaO and MgO supported Ni catalysts. The catalysts were prepared by the impregnation method. The reaction was carried out at 1 atm, 750 ℃, and CH4: O2=2 : 1. 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 reaction mechanism of this reaction, the temperature of the catalyst bed at top and bottom of the bed were measured with pulses of the reactants (CH4 : O2=2:1); the changes in the moles of the reactants and products were determined with time; and O2-TPD experiment was carried out. From the results, it is deduced 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 give synthesis gas.