To investigate the long afterglow properties of the samples, long persistence phosphors of SrAl2O4∶Eu2+,Dy3+ are successfully synthesized and the samples are irradiated by irradiation, which is from the 60Co~γ source and whose dose is accumulated to 100 kGy. The influence of irradiation on the properties of these two kinds of phosphors is studied by comparing crystal structure, optical adsorption properties, decay curve and thermoluminescence (TL) characteristics of unirradiated and irradiated samples. X-ray diffraction (XRD), Raman spectrometer, ultraviolet visible spectrophotometer, fluorescence spectrophotometer and thermoluminescence spectrometer are used to investigate these properties. Conclusions from the present work can be briefly summarized as follows. In irradiated samples, the unit cell volume decreases and the concentration of oxygen vacancies increases after irradiation. The absorption intensity of irradiated samples rises because of more irradiation-induced defects introduced. The decay time is prolonged and the initial brightness is promoted after irradiation. Thermoluminescence studies reveal that thermoluminescence glow peak of irradiated sample shifts towards higher temperature and its intensity is improved greatly. It is calculated that the depth of traps increases 0.0039 eV after irradiation, which demonstrates that the irradiation not only affects the traps′ distribution but also increases the number of deeper traps.