Tellurite oxyfluoride glasses with composition of 71TeO2-10ZnO-10BaF2-4K2O-3Nb2O5-2TiO2 doped with different concentrations of DyF3 (0.3, 0.4, 0.5, 0.7, 1 wt%) were prepared by melt-quenching method under dry O2 atmosphere. Under 808 nm laser pumping, infrared (IR) fluorescence emission with central wavelength of 2.86 μm was detected. Basing on the Judd-Ofelt (J-O) theory, the intensity parameters (Ωλ, λ=2, 4 and 6) and radiative property were calculated and characterized through the transmission and fluorescence spectra. The tellurite oxyfluoride glass had high thermal stability and large emission cross-section at 2.86 μm (7.82 × 10−21 cm2). DyF3 doped tellurite oxyfluoride glass ceramic were prepared via in-situ crystallization of ZnTe nanocrystals through heat treatment to ameliorate the surrounding environment of rare earth (RE) ions. The tellurite oxyfluoride glass ceramic prepared by heat treatment at 390°C had great enhancement in 2.86 μm fluorescence intensity (about 7 times), longer fluorescence lifetime (126 μs), indicating that the in-situ crystallization method may be helpful for exploring tellurite based high gain laser glass. © 2021