The Er3+-doped 70TeO2-(25x)B2O3-xGeO2-5Na2O(x=5,10,15,20 mol%) tellurite-borate glass series are prepared by conventional high-temperature melting and annealing method.In order to enhance the fluorescent intensity of 1.53 μm band the absorption spectra,infrared transmission spectra and lifetimes of the 4I13/2 level of Er3+ are measured,and the spectroscopic properties of Er3+ are analyzed at different composition cotents of glass hosts with the help of Judd-Ofelt theory.Moreover,the effects of O...