A Ni catalyst supported on mono dispersed silica spheres, Ni/SiO2-Sph (SG), has been successfully synthesized by a sol gel method. By comparing it with other Ni catalysts (supported on commercial silica and silica spheres) prepared by an impregnation method, we find that the size of Ni particles and their dispersion are closely related to performances of the catalysts in partial oxidation of methane (POM) into synthesis gas (CO + H-2). Several means such as H-2-TPR, TEM, and XRD are employed to characterize these catalysts. Although the catalyst Ni/SiO2-Sph (SG) in specific surface area is not large, the Ni particles are the smallest in size (3-5 nm) among the three catalysts, and are uniformly distributed, high dispersed over the silica surfaces, being not much changed as Ni loading. It is notable that the smaller size of the NiO particles is corresponding to the stronger NiO-SiO2 interactions. The catalyst Ni/SiO2-Sph (SG) shows the best catalytic performances and the longest lifetime among the three catalysts at the POM conditions. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.