In order to optimize the processing parameters of nanostructured coating during laser cladding, the changes of nanoparticles size under high energy density laser are investigated. Based on the Brook′s classical theory about grain growth and temperature field of laser cladding with finite element software Ansys, the nanoparticles growth of laser-clad nanostructured Al2O3+13%TiO2 (mass fraction) coating prepared by plasma spraying are investigated. The effects of nanoparticles original size and laser-cladding region on grain growth are studied. Meanwhile, experiment of laser cladding on nanostructured Al2O3+13%TiO2 prepared by plasma spraying is carried out. The results show that the experimental overall trend of nanoparticles growth is consistent with the calculated result during laser cladding process, which indicates that the nanoparticles growth theory based on Brook′s theory is correct and reliable. The theory provides theoretical basis for nanoparticles growth during laser cladding process.