Transparent glass ceramics containing YF 3 nano-crystals were fabricated by heat treatment of the SiO 2 –Al 2 O 3 –NaF–YF 3 –LnF 3 (Ln=Er, Yb) glasses. X-ray diffraction and transmission electron microscopy analyses evidenced the homogeneous distribution of spherical YF 3 nano-crystals sized 25–30nm among the glassy matrix. Energy dispersive X-ray spectroscopy measurement, combined with the Stark splitting of the absorption and emission bands, verified the incorporation of Er 3+ and Yb 3+ ions into YF 3 nano-crystals. The infrared to visible up-conversion emission of Er 3+ intensified with the increasing of Yb 3+ concentration, ascribing to the increase of the efficiency of non-radiative energy transfer from Yb 3+ to Er 3+ which exceeded 45% for the 0.5Er 3+ /1.0Yb 3+ co-doped sample. The up-conversion luminescence at 545 and 660nm were affirmed coming from two-photon excitation process.