NaYbF4∶0.01%Tm3+,20%Eu3+ nanocrystals were synthesized by hydrothermal method.The crystalline phase,morphology,and optical properties were characterized by X-ray diffraction,scanning electron microscope and luminescent spectra.The samples are nano-rods with uniform size distribution.Their length is 500 nm and diameter is 200 nm on average.Under 980 nm near-infrared laser excitation,ultraviolet and visible upconversion luminescence of Eu3+ was obtained.In the codoped NaYbF4 nano-rods,the energy transfer from Tm3+ to Eu3+ and the bridging effect of Tm3+ ions play important roles in populating the high-energy excited states of Eu3+.Furthermore,the upconversion emissions from 3P0→7Fj(j=0,1,2) of Eu3+ were observed for the first time.