Alkali oxides K2O, Na2O and alkaline-earth oxides CaO、 SrO、 BaO, and La2O3, Al2O3、 B2O3 are used in Yb³⁺-doped silicate glasses, their effects on physical and spectroscopic properties are studied, especially the lifetime and stimulated emission cross-section. Effect of radiation trapping on measured fluorescence lifetime is considered. Explanation of lifetime quenching in case of high level Yb3+-doped glasses is given and relative long lifetime and large stimulated emission cross-section are obtained in our experiments.