In order to investigate the mechanism of energy transfer and fluorescence properties of Sm3+/Eu3+ co-doped system,the samples of Sm3+/Eu3+co-doped in LaOF nanocrystals were synthesized by using a hydrothermal-sintering technique.The characterization results of XRD and TEM show that the structure of the nanocrystals is hexagonal,and its size is about 70 nm.Using 442 nm laser to pump the LaOF:Sm3+/Eu3+ nanocrystals,the energy transfer effect from Sm3+ ions to Eu3+ ions was completed,and the fluorescence emissions originating from the 5D0 level of Eu3+ were observed.The luminescence properties of the LaOF:Sm3+/Eu3+ nanocrystals system were analyzed with a spectroscopic method.It was found that the energy transfer results from the relaxation from the 4G5/2 state of Sm3+ ions to the 5D0 state of Eu3+ ions,and the efficiency of the energy transfer increases with the increase of the concentration of Eu3+ ions.