Ru nanoparticles supported on carbon nanotubes showed efficient reactivity for hydrogenolysis of aqueous glycerol solution to produce glycols of 1,2-propanediol and ethylene glycol. The glycerol conversion along with the product selectivity depended essentially on the mean size of Ru nanoparticles. The Ru mean size around 5 nm showed the highest yield of glycols. The results indicated that the hydrogenolysis of glycerol catalyzed by the supported Ru nanoparticles might be structure-sensitive.