Spectral properties of bismuth-doped optical fiber developed independently are experimentally and theoretically studied. The four absorption peaks centered at 494, 816, 946 and 1410 nm are observed in the absorption spectrum of the fiber. Using the Giles model, the amplification characteristics of the fiber are studied, and the influences of fiber length, pump power and input signal power on the gain and noise figure are analyzed. In the steady state, the rate equations and propagation equations of three-level model are established and calculated by means of Runge-Kutta method. The results show that when the bismuth-doped optical fiber is pumped at 830 nm and 200 mW in power, gain coefficients between from 1384 nm to1480 nm are large than 1.5 dB/m and the noise figures are nearly 5 dB.