Absorption and emission properties of Yb 3+-doped fluoroaluminate glasses were analyzed according to the measured absorption and emission spectra. The emission cross section of Yb 3+ ions was calculated. The fluorescence reabsorption effect and concentration quenching effect of Yb 3+ ions were discussed. Difference between measured emission section and calculated emission section of Yb 3+ was caused by the reabsorption effect, which also decreased the fluorescence intensity of Yb 3+ ions. The energy transfer from Yb3+ ions to Er3+ ions was the second key factor leading to concentration quenching in heavily Yb3+-doped fluoroaluminate glass.