Abstract: The effects of MgO promoter on the physicochemical properties and the catalytic performance of Ni/Al2O3 catalysts for partial oxidation of methane to syngas were studied by BET, XRD, H2 TPR, TEM and reaction activity evaluation. It was found that MgO promoter benefited to the uniformity of nickel species on the catalysts, inhibited the formation of NiAl2O4 spinel and improved the interaction between nickel species and the support. This result was related to the formation of NiOMgO solid solution and MgAl2O4 spinel. Moreover, for the catalysts with proper amount of MgO promoter, the dispersion of nickel species was enhanced, and thus their catalytic performance for methane partial oxidation to syngas was improved. However, excessive MgO promoter exerted a negative effect on the catalyst performance. In addition, the basicity of MgO promoted the reverse watergas shift reaction, which led to the increase of CO selectivity and the decrease of H2 selectivity. The suitable content of MgO promoter in Ni/Al2O3 catalyst was about 7%.