Abstract: The rare-earth doped afterglow phosphors Sr_0.9M_0.1Al₂O₄ : Eu²⁺, Dy³⁺ (M=Mg, Ca, Ba) were synthesized by a high temperature solid-state reaction method. Crystal structure, spectrum properties, afterglow performance of the samples was analyzed. X-ray diffractometry (XRD) patterns indicated that the crystal structure was not changed with some Mg²⁺, Ca²⁺, Ba²⁺ taking the place of Sr in SrAl₂O₄. Spectrum measurements showed that the excitation spectrum is a wide excitation band at 250~450 nm after Mg²⁺, Ca²⁺, Ba²⁺ taking the places, and excitation peaks were observed in the excitation spectrum at 266, 320, 360, 416 nm. The wavelength has a little blue shift with Mg²⁺ and Ba²⁺ instead and has a little red shift with Ca²⁺ instead. Afterglow testing observed that the afterglow time is longer with Ca²⁺ instead than Mg²⁺, Ba²⁺ instead.