A novel Er³⁺-doped tellurite glass with compositions of TeO₂-ZnO-Na₂O-Bi₂O₃ was prepared,and the intensity parameters,spontaneous emission probability,absorption and emission cross-section of Er³⁺ ions were calculated according to the Judd-Ofelt and McCumber theory. The signal gain characteristics of fiber amplifier with this erbium-doped tellurite glass fiber as a gain media were investigated based on a four-level population rate-light power propagation equation model pumped at wavelength of 1480 nm,in which energy up-conversion,cross relaxation,excited state absorption and amplified spontaneous emission noise of Er³⁺ions were considered. It is shown that the tellurite glass fiber prepared here presents a bigger signal gain and wider gain spectrum,its maximum signal gain and gain width at 20 dB exceeds 40 dB and 80 nm respectively,and its gain spectrum can across the C+L band region when pumped at 200 mW and injected with-30 dBm×56channels signal. The results indicate that the erbium-doped tellurite glass is a kind of better gain media which can be applied to broadband amplifiers. Moreover,the fiber structural parameters such as fiber length,fiber radius and relative index difference will have much affects on its gain characteristics.