A novel white light emitting long lasting phosphorescent material Ca3SnSi2O9: Dy3+ was synthesized by conventional solid-state reaction method. It shows a white light emitting phosphorescence at room temperature after the 254 nm UV light irradiation stopped, and it is considered that the phosphorescence originates from the mixture of Dy3+ characteristic luminescence. The thermoluminescence (TL) spectra show that Dy3+ ion induces a proper trap in the phosphor with the depth of 0.402 eV and results in long afterglow phosphorescence.