Yb3+/Er3+ ions codoped bulk glass ceramics (GC) with embedded monoclinic K3LuF6 nanocrystals are reported for potential temperature-sensing application by using the fluorescence intensity ratio method. Such GC with good transparency and enhanced up-conversion were prepared by the simple conversional melt-quenching method and subsequent annealing process. Optical, structural, and temperature-sensing up-conversion properties were characterized systematically. Optical spectroscopy analysis confirms the incorporation of Yb3+/Er3+ into the K3LuF6 crystalline lattice, resulting in enhanced up-conversion luminescence. Compared to other Er3+-doped typical systems, Er3+ ions in K3LuF6 GC present large energy gap (870cm(-1)) and high relative sensitivity (37.6x10(-4)K(-1) at 625K), revealing that K3LuF6:Yb3+/Er3+ GC can be excellent candidates for optical thermometers.