Ceria nanoparticles have been proved to be one of the most promising optical conversion host structures, due to its low-phonon nature and non-stoichiometric structure. In up-conversion, erbium has been extensively used as the main optical center for converting low-photon energy into higher ones. This paper studies the effect of introducing plasmonic nanostructure, such as gold, for enhancing the optical upconversion quantum yield efficiency of erbium-doped-ceria nanoparticles. The numerical results show that the efficiency experienced a significant enhancement as a result of existence of metal nanostructures. In addition, the temperature influence upon the nanocomposite is studied in detail. The numerical calculations show that the temperature change has a remarkable influence on the luminescence parameters and quantum yield efficiency of the up-conversion structure.