Abstract: The relation bewteen properties of Eu²⁺ and Dy³⁺ co-doped strontium aluminate phosphor and Al/Sr ratio was investigated,A series of strontium aluminate phosphors with different Al/Sr ratios from 1.8 to 2.7 were synthesized by solid state reaction method.The crystal structures were characterized by X-ray,The emission and afterglow spectra were investigated by fluorescence spectrophotometer.The results showed that,the matrix phase according the order by SrAl₂O₄→ Sr₂Al₆O₁₁→Sr₄Al₁₄O₂5.Moreover,the emission spectra of the samples shift to blue-green short wavelength from yellow-green long wave with the increase of Al/Sr ratios,which result from change of products composition.