The influence of Ce 3+ ions on the spectroscopic properties of Er 3+ doped tellurite glass was investigated in this work. It is found that the fluorescent intensity of 4I 13/2 level of Er 3+ ion is enhanced, stimulated emission cross section and FWHM of fluorescent peak are increased and upconversion intensity under 980 nm excitation is greatly suppressed in Er 3+ doped tellurite glass. This affect is due to energy cross relaxation from 4I 11/2 level of Er 3+ to 2F 7/2 level of Ce 3+ . Through empirical equation calculation, it is found that the lifetime of 4I 11/2 level of Er 3+ is greatly decreased by Ce 3+ co doping, while the lifetime decrease of 4I 13/2 is very small.