Oxynitride long-lasting phosphorescence (LLP) phosphor SrSi2O2N2:Eu2+ was prepared by a new method using SrSi alloy as a precursor. Its properties were systematically investigated utilizing XRD, photoluminescence, excited-state decay curve, long-lasting phosphorescence, and thermoluminescence spectrum. This phosphor was found to be well-crystallized by calcinations of the Sr1-xEuxSi alloy and the SiO2 mixture at 1400 degrees C for 3h. After irradiation under the 280nm UV light, the afterglow emission of Eu2+ (4f65d1 4f7) was obviously observed for at least 2h in the limit of light perception of dark-adapted human eyes (0.32mcd/m2). Furthermore, the possible mechanism for the LLP of SrSi2O2N2:Eu2+ phosphor is also discussed in this article.