The thermal stability and spectroscopic properties of Er2O3-doped TeO2-GeO2-ZnO-Na2O-Y2O3 glasses for 1.5 mum fiber amplifiers were investigated. The thermal stability of the 75TeO(2). 20ZnO . 5Na(2)O glass was improved by introducing GeO2 and Y2O3. The radiative transition and the nonradiative transition have a dominant influence on the I-4(13/2) level lifetime of Er3+ in high- and low-GeO2 regions, respectively. Adding Y2O3 increases tile I-4(13/2) level lifetime of Er3+ significantly. The Judd-Ofelt (J-O) parameter Omega (6) shows a strong correlation with the 1.5 mum emission bandwidth; and the larger the Omega (6), the wider the bandwidth.