Sintered ceramics of -Sr2SiO4: Eu2+, R3+(R=Tm, Gd) were prepared and their spectroscopic properties were evaluated. A large enhancement of green photostimulated luminescence (PSL) was observed from -Sr2SiO4:Eu2+ codoping with Tm3+ at a recognizable intensity level, and the most efficient PSL was obtained when the codoping concentration of Tm3+ was 0.002. It was proved that the introduction of Tm3+ created a large number of oxygen vacancies which serve as traps for electrons excited by UV irradiation. In addition, a distinguishable difference between the photoluminescence (PL) and PSL spectra of -Sr2SiO4: Eu2+, Tm3+ was observed, namely the PSL spectrum exhibits only a symmetric emission band peaked at about 540nm while both 470 and 540nm peaks were detected in the PL spectrum. It is safe to say that PSL only derives from one emission center of Eu2 in the crystallographic Sr2 sites, which could be ascribed to the different distribution of trap centers for two crystallographic Sr sites.