Er3+-doped tellurite glasses with composition in mol percent of 70TeO2-20(ZnO, WO3, AlO1.5)-9NaO0.5-1ErO1.5 were prepared by conventional melt-quenching method. The absorption spectra and the fluorescence spectra of the glasses were measured, and the thermal stability of the glasses was measured by the Differential Thermal Analysis (DTA) technique. The glass internal structure was analyzed, and the bandwidth quality factor ( σepeak × FWHM ) and gain quality factor σ were compared among the three glasses based on the intensity parameters. t (t=2, 4, 6) calculated by (mpeakeτ×) Judd-Ofelt theory, and the Er3+ absorption cross-section and stimulated emission cross-section calculated by McCumber theory, respectively. The results show that the bandwidth quality factor can be enhanced by 1.3 and 1.6 times, and the gain quality factor can be enhanced by 1.2 and 1.4 times when the composition ZnO in the tellurite glass was replaced by WO3 and Al2O3, respectively. Furthermore, the thermal stability was increased evidently in the glass containing Al2O3. The studies indicate that the spectral properties and thermal stability of Er3+-doped tellurite glass can be improved through the change of glass constituent.