New data about influence of ceramic nanoparticles additives on the hard metals WC-Co properties using calculated and experimental methods are received. The final physical and mechanical properties of hard metals modifying  by nanoparticles depend of  their microstructural parameters, proportion of volume ratios and size of carbide and ultrafine particles. Nanoparticles introduced into a binder size decrease of the metal interlayer and therefore increase the strength of binder and composite as a whole. The reduction of the carbide grain average size was found out as well (owing to   nanoparticles blocking influence on recrystallization).