Irradiation treatments on glasses in both PbO-B2O3-SiO2 and Bi2O3-B2O3-SiO2 systems were carried out under the 60Co gamma-ray radiation at a dose of 5.0 kGy. Ultraviolet and visible (UV-Vis) transmission spectra were used to compare the optical transmittance before and after irradiation in the wavelength range of 300-800 nm. The radiation-induced absorption coefficient (RIAC), the optical mobility gap (E-0), and the width of the energy tail above the gap (Delta E) were calculated by optical transmittance. The variation of these parameters indicated that the structure of glasses changed due to irradiation. The differences in the optical properties of the two glass systems were explained from the viewpoint of glass chemistry.