The luminescent properties of Sr2.97MgSi2O8：Eu^2＋0.1 phosphors were investigated with different Ln^3＋0.02（Ln^3＋： Dy^3＋, Er^3＋, Ho^3＋） co-dopants. The co-dopants had no influence on both the structure of the lattice and the position of the emission peak. However, the afterglow properties of samples were enhanced with different co-dopants. The afterglow duration of the Dy^3＋ co-doped sample was longer than that of the others. Furthermore, the co-doping samples had stronger thennolmninescence （TL） intensity and therefore longer afterglow duration. At last, the self-reduction of Eu^3＋→Eu^2＋ was observed in an silicate compound of Sr3 xMgSi2Os：xEu phosphor in air condition. This is the first time to show a blue long afterglow phosphor synthesized avoiding reducing atmosphere.
