Na(Gd-x,Y1-x)F-4(x=0, 0.3, 0.5, 0.7 and 1) solid-solution nanocrystals precipitated from glasses were prepared for the first time by conventional melting-quenching technique and subsequent heat treatment. Using Er3+ as a structural probe, the partition of lanthanide activators into the Na(Gd-x,Y1-x)F-4 lattice was evidenced. The types and distribution of crystallite were determined by XRD, TEM. We also studied the upconversion luminescence property of Er3+ in Na(Gd-x,Y1-x)F-4. The atomic radius plays an important role in luminescence properties of substitution solid solubility. The atomic radius of Er is more closer to Gd compared with Y through our theoretical calculation, which resulted that Er ions replace Gd ions from NaGdF4 is easier than Er ions replaced Y from NaYF4. Therefore, the intensity of emission can be enhanced significantly when the precipitation crystal from NaYF4 turn into NaGdF4. (C) 2016 Elsevier Ltd. All rights reserved.