In this paper, we report on the radio-photoluminescence (RPL) properties and RPL center formation mechanism in Ag-doped Na–Al borate glass (BG:Ag). In BG:Ag, broad emission bands at 550–800 and 450–800 nm with excitation wavelengths at 320 and 360 nm appeared after X-ray irradiation, respectively. The electron spin resonance (ESR) signal intensity of Ag2+ and Ag2+ increased with absorption dose. These results suggest that BG:Ag exhibits RPL from Ag2+ and Ag2+. Furthermore, RPL emission bands and the ESR signals of Ag2+ and Ag2+ disappeared after heating at 773 K for 1 h. These results indicate that RPL centers can be eliminated by heating and that BG:Ag is a candidate reusable RPL material. On the basis of the variation of the ESR spectra with time from immediately after irradiation, we assumed the following RPL center formation mechanism. First, electron–hole pairs are generated by ionizing radiation. Some of the electrons are trapped at Ag+ and form Ag0. Subsequently, Ag2+ ions are formed by the association of Ag+ and Ag0. On the other hand, holes are trapped at the boron-oxygen network to form a boron oxygen hole center (BOHC). Subsequently, the trapped holes transfer to Ag+ from BOHC and form Ag2+.