A series of Er3+/Tm3+ codoped tellurite glasses are prepared using the high-temperature melt-quenching method and the 1.85 μm band infrared spectroscopic properties of Tm3+ under the 800 nm LD excitation are investigated by measuring the differential scanning calorimeter (DSC) curves, absorption spectra, fluorescence spectra and fluorescence decay curves of glass samples, together with the calculations of the Judd-Ofelt intensity parameters, spontaneous radiative transition rates and radiative lifetimes of Tm3+ ions. The results show that the Er3+/Tm3+ codoped tellurite glasses have good thermal stability and the 1.53 μm band fluorescence intensity of Er3+ ions decreases rapidly, while the 1.85 μm band fluorescence intensity of Tm3+ ions increases accordingly with the increase of Tm3+ ion doping concentration. The analysis of 1.85 μm band luminescence processes indicates that the improvement of the infrared fluorescence intensity of Tm3+ can be attributed to the comprehensive energy transfers of Tm3+3H4→Er3+4I9/2, Er3+4I11/2→Tm3+3H5, and Er3+4I13/2→Tm3+3F4, and the micro-parameters, critical radius and phonon contribution for the above energy transfer processes are calculated and analyzed further. The research demonstrates that the Er3+/Tm3+ codoped tellurite glass is a promising host material applied for the 1.85 μm band fiber lasers.