Er~(3+)/Yb~(3+) co-doped 70TeO_2-5Li_2O-(25-x)B_2O_3-xGeO_2(x=0,5,10,15,20 mol%) glasses were prepared. The thermal stability of glasses were studied. The absorption spectra,emission spectra and fluorescence lifetime of the 4I_ 13/2 level of Er 3+ ions were measured. The stimulated emission cross-section of 4I_ 13/2 → 4I_ 15/2 transition was calculated on the basis of McCumber theory. The results show that with increasing GeO_2 content in the glass composition, the thermal stability, fluorescent intensity and lifetime of the 4I_ 13/2 level of Er 3+ ions increase, while fluorescence full width at half maximum (FWHM) is fixed at about 70 nm. The obtained data suggest that the system of these glasses can be used as a suitable candidate host material for potential broadband optical amplifier.