Strontium aluminate-based phosphors SrAl2O4:Eu2+,Dy3+ (SAO-ED) are coated directly by the interfacial coordination chemistry method with maleic anhydride to prevent their hydrolysis in moist air. SEM, XPS, TG and DSC methods are used to characterize the coating. The results showed SAO-ED phosphors coordinated with maleic anhydride by the coordination bond and . The introduction of maleic anhydride doesn’t change the excitation and emission spectra of SAO-ED phosphors, which is proved by the photoluminescence measurement. The SAO-ED phosphor coated with 30 wt. % maleic anhydride has higher water-resistance at the cost of a minor loss of persistent phosphorescence than that of SAO-ED phosphor.