Sodium and aluminum fluorides coated BaF2 was synthesized by hydrothermal method. It was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and fluorescence spectrophotometer, respectively. The analysis results indicated that sodium and aluminum fluorides existed in the form of sodium fluoride and sodium fluoroaluminate, which combined with BaF2 surface via chemical bonds, and exhibited coated structure. Fluorescence spectroscopy testing showed that there were two wide upconversion emission peaks with maxima at 304 and 324 nm under the excitation at 583 and 863 nm, respectively. Its phosphorescence life time was greater than 18.4 ms, and the emission intensity exhibited a rising process from the beginning and a decaying process after 15 ms. The luminescence mechanism was proposed according to the energy conversion process of the upconversion emission, the results showed that the upconversion emission belonged to the quantum confinement effect-interface light emission center radiative recombination.