Ni catalysts supported on mesoporous silica KIT-6 with and without promoters (La, Mg and Mo) were prepared by co-impregnation and their catalytic performances on CO methanation were conducted in fixed-bed reactor. As a result, promoters had a negligible benefit to the dispersion of Ni particles since Ni species were highly dispersed on KIT-6. While the metal Ni surface area was reduced due to partial coverage of metal Ni by promoters. Besides the improvement of the promoters (La and Mo) on CO methanation activity, a suitable Ni- support interaction can hindrance the aggregation of Ni particles on 0.5MoNi/KIT-6 during thermal treatment. While the aggregation of Ni particles was severe on Ni/KIT-6 and 0.3LaNi/KIT-6 due to the weak interaction between Ni and support. Furthermore, Mg enhanced the interaction between Ni and KIT-6 by forming NiO-MgO solid solution, but simultaneously some "unsupported" free and "surface rich" Ni species was formed, which would aggregate into larger particles (ca. 25 x 40 nm) during thermal treatment. It was worth mentioning that high pressure (3 MPa) improved the catalytic activities and thermostability of catalysts for CO methanation but the aggregation of metal particles were more severe after thermal treatment in reactants under high temperature.