Yb-doped double-clad fibers are prepared through a conventional modified chemical-vapor deposition technique and solution doping method: each fiber contains a core of around 10 μm in diameter. These fibers are divided into groups under 60Co γ radiations of different doses, and we investigate the fiber absorption spectra and laser spectral properties before and after irradiation. Experimental results show that with increasing the irradiation dose the absorption of the fiber after irradiation increases significantly in the visible region, we believe that the enhancement of optical fiber absorption in the visible region may be due to the color center defects existing already in the fiber (such ODC (Ⅱ)) and the color center defects produced by the irradiation (E'center, POR and Yb2+ions). We also analyze slope efficiencies, bare efficiencies, and transmission characteristics of the fiber before and after laser irradiation. Finally, we use the power-law to fit the radiation-induced losses of the fiber under different radiation doses, and the results obtained in this paper provide a theoretical basis for studying the anti-radiation of optical fibers.