Abstract This papers presents the effects of Co-60 gamma irradiation on the absorption loss of single mode optical fibers doped with rare earth Er3+. The parameters of optical fibers are measured, prior to irradiation and after irradiation and UV bleaching. It has been found that absorption loss in the wavelength range of 0.80-1.60μm is greatly lager than those of unirra-diated fibers. Its increase law of absorption loss is similar to that of β ray irradiation. This similarity can be explained by Compton's effect. The induced loss can be partly bleached by UV, resulting in a better effect than heat annealing. In order to improve radiation resistivity, the elements with smaller atomic number should be selected as dopants in both core and cladding of the fiber.