A gamma irradiation experiment is conducted on erbium-doped fiber, and its′ absorption and emission cross sections are calculated according to measured absorption and emission coefficients of erbium-doped fiber before and after irradiation. Radiation models of absorption and emission cross sections are built up based on power law model. Radiation effects on the output spectrum shape and characteristics parameters of erbium-doped fiber source are simulated and analyzed based on the radiation models of absorption and emission cross sections being put into the model of erbium-doped fiber source. The simulation results show that after gamma irradiation, the output power of source decreases from 9.32 mW to 4.30 mW, the mean wavelength moves from 1531.60 nm to 1531.19 nm, and the band width varies from 8.79 nm to 6.78 nm. Finally, the simulation results are verified experimentally.