This paper investigated the MIR emission of Ho 3+ -doped Ge 20 Ga 5 Sb 10 S 65 chalcogenide glasses upon excitation of 900nm laser diode. The spontaneous emission probability, absorption cross-section, and emission cross-section were calculated using the Judd-Ofelt theory and the Fuchbauer–Ladenburg equation. Theoretical studies of the Ho 3+ -doped chalcogenide glass fiber amplifier operating in the MIR wavelength range, specifically around the 2.86μm wavelength, were performed based on the rate and light propagation equations. The results indicate that the chalcogenide glass fiber presented a larger signal MIR gain and wider MIR gain spectrum. The maximum signal gain was 36dB and the gain width was 20dB.