Gd2O2S: Eu, Mg, Ti, a novel red long afterglow phosphor, was synthesized in microwave field. The synthesized phosphors were investigated respectively by XRD, SEM and fluorescence spectrophotometer. The results show that Gd2O2S: Eu, Mg, Ti phosphors possess hexagonal crystal structure, which is similar to that of Gd2O2S. The particles of Gd2O2S: Eu, Mg, Ti phosphors are basically spherical in shape, with good dispersing. The mean particle size is 1-2 microm. The excitation spectrum is a broad band and the main peak is at 360 nm. Moreover, excitation peaks at 400, 422 and 472 nm were found in the excitation spectrum. The emission spectrum shows that Gd2O2S: Eu, Mg, Ti has narrow emission peaks. The emission peaks are ascribed to Eu3+ ions transition from 5 D(J) (J = 0, 1, 2) to 7F(J) (J = 0, 1, 2, 3, 4). With the increase in Eu3+ molar ratio, the emission peaks at 586, 557, 541, 513, 498, 471 and 468 nm in the blue and green region weaken gradually relative to the main emission peak at 627 nm. Therefore the red emitting at 627 nm becomes strong gradually. When the molar ratio is 6%, the red emitting becomes the strongest. The Ti and Mg co-doping can obviously improve its long-afterglow property.