A model of Er³⁺-doped chalcogenide glass (Ga₅Ge₂₀Sb₁₀S₆₅) microstructured optical fiber (MOF) amplifier under the excitation of 980 nm is presented to demonstrate the feasibility of it applied for 1.53 μm band optical communications. By solving the Er³⁺ population rate equations and light power propagation equations, the amplifying performance of 1.53 μm band signals for Er³⁺-doped chalcogenide glass MOF amplifier is investigated theoretically. The results show that the Er³⁺-doped chalcogenide glass MOF exhibits a high signal gain and broad gain spectrum, and its maximum gain for small-signal input (?40 dBm) exceeds 22 dB on the 300 cm MOF under the excitation of 200 mW pump power. Moreover, the relations of 1.53 μm signal gain with fiber length, input signal power and pump power are analyzed. The results indicate that the Er³⁺-doped Ga₅Ge₂₀Sb₁₀S₆₅ MOF is a promising gain medium which can be applied to broadband amplifiers operating in the third communication window.