The fluorescence properties of 2.7μm emission and energy transfer mechanism of Ho 3+ /Er 3+ co-doped fluoride glass (ZBYA) have been investigated in the present paper. Ho 3+ strengthens the Er 3+ : 2.7μm emission in the ZBYA glasses due to the energy transfer from Er 3+ to Ho 3+ , while the 1.5μm emission decreases dramatically. The optimized concentration ratio of Er 3+ to Ho 3+ is found to be 1:1 in our glass system. The absorption and emission spectra are tested and the sample possesses large emission cross section (16.5×10 −21 cm 2 ) around 2.7μm along with larger radiative transition probability (25.11S −1 ) on the basis of Judd–Ofelt and Fuchtbauer–Ladenburg theories. Additionally, the energy transfer microparameters are calculated using Förster–Dexter theory and the result shows the energy transfer coefficient of Er 3+ : 4 I 13/2 →Ho 3+ : 5 I 7 is 24 times larger than that of Er 3+ : 4 I 11/2 →Ho 3+ : 5 I 6 . Our results show that Er 3+ : 2.7μm emission can be sensitized by Ho 3+ efficiently, and this Er 3+ /Ho 3+ -codoped fluoride glasses might have potential application in mid-infrared lasers.