The effects of inert particles on the liquid hydrogenation over nano-sized Ni-B catalysts were investigated in a batch reactor. Nitrobenzene hydrogenation was used as a test reaction. The effects of stirring speed and the dispersant/catalysts ratio were investigated. Addition of inert particle in the reaction system of nano-catalysts could increase the reaction conversion significantly. The reaction conversion increased with increasing stirring speeding until 900 rpm, and then decreased. The addition of inert particle to the reaction system could prevent the agglomeration of nano-metals and disperse them over the entire reaction system. Nano-metals were physically attached on the external surface of the inert particles. In addition, the addition of inert particle may enhance the absorption rate of hydrogen in solvent, and resulting in the increase of reaction rate. Both are beneficial to the reaction conversion. The enhancement effect of Al2O3 is much greater than that of SiO2.