Long-lasting phosphor Y2O2S∶Eu3+, Mg2+, Ti4+ was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu2O3 content in Y2O2S∶Eu3+x(0.01≤x≤0.10). On the other hand, the change of unit cell parameter a is not linear dependence. In the Y2O2S∶ Eu3+ crystal structure, Eu3+ ions only replaced Y3+ ions′ places in which it posited center position of c axis. With the increase of Eu2O3 content, the position of the strongest emission peak changed from 540 nm (5D1→7F2 transition) to 626 nm (5D0→7F2 transition), and the maximum intensity was obtained when x=0.09 in Y2O2S∶Eu3+x(0.01≤x≤0.10). This is due to the environment of trivalent europium in the crystal structure of Y2O2S. Doping with Mg2+ or Ti4+ ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg2+ and Ti4+ ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence (LLP) was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye (0.32 mcd*m-2). Thus the LLP mechanism was analyzed.