Er3+ ion doped glass samples with different doping ratio of NaF and YF3 were prepared with traditional melt cooling technology and all samples were cut into small piece of about 15 mm×15 mm×3 mm for polishing process. The glass transition temperature (Tg) and obvious crystallization peaks were determined by differential thermal analysis. The glass samples were heated at 600 ℃ for 2 h. After the thermal treatment, some intensity diffraction peaks correspond to cubic NaYF4 nanocrystals with different size. The size and distribution of the crystallites were determined by XRD, TEM and EDX analysis of glass ceramic samples. From fluorescence spectra and absorption spectra of glass ceramic samples, the color was changed. In the result of crystallization activation energy, it can be determined that glass network structure can be influence by NaF. When the content of NaF is low, integrity of glass network structure is high, and the crystallization activation energy of glass is increased. So the crystallization ability of glass is reduced. From the result of experiments, when the content of NaF is higher, the size of crystals is bigger, the concentration of Er3+ ions in the crystal is higher. And the same time the phenomenon of cross relaxation between Er3+ and Er3+ will be enhanced. It will be caused red emission of Er3+ stronger. Correspondingly, When the content of NaF is reduced, the size of crystals is smaller, the concentration of Er3+ ions in the crystal is lesser. the phenomenon of cross relaxation between Er3+ and Er3+ will be weakened. At this time, the sample will realize green emission. In this paper, the luminous of glass ceramic with Er3+ doped is adjusted successfully by changing the size of crystals.