Graphene oxide/GdF3: Yb, Er (GO/GdF3) nanocomposite have been successfully synthesized via a facile low-temperature hydrothermal route, in which fusiform orthorhombic phase GdF3: Yb, Er nanocrystals with uniform size could grow in the graphene oxide substrate. During the annealing of GO/GdF3 nanocomposites, a structure change from GO/GdF3 nanocomposites to reduced graphene oxide/NaGdF4: Yb, Er (rGO/NaGdF4) nanocomposites was discovered by X-ray powder diffraction, Fourier transform infrared spectroscopy, Thermogravimetric analysis and Scanning electron microscope. Under the excitation of 980 nm, the upconversion luminescence of GO/GdF3 was completely quenched by the energy receptor in GO substrate, however the black rGO/NaGdF4 showed improved green upconversion luminescence. Based on the analysis of energy transfer in the nanocomposites, the improvement of the upconversion luminescence of the rGO/NaGdF4 can be attributed to the structure change of nanocomposites. (C) 2016 Elsevier Ltd. All rights reserved.