A series of novel long-lasting phosphors, Sr3Al10SiO20:Eu2+,RE3+, were prepared and studied. Under UV irradiation, broad-band emission long-lasting phosphorescence located at 466 nm was observed in all of these phosphors at room temperature. The effects of RE3+ as a co-dopant in Sr3Al10SiO20:Eu2+ were discussed in conjunction with the afterglow decay curves and thermoluminescence (TL) spectra. Quantitative TL spectra revealed that the introduction of RE3+ ions into Sr3Al10SiO20:Eu2+ host produces a highly dense trapping level at appropriate depth (335 K), which is considered to be responsible for the long-lasting phosphorescence at room temperature.