Long lasting strontium aluminate phosphors were synthesized by means of coated precipitation in the experiment. SrAl2O4 monoclinic phase with long afterglow was synthesized at 1 100 ℃ with the aid of H3BO3, and the synthetic temperature decreased about 100 ℃-150 ℃ than in solid state reaction. The process of heat treatment was studied by TG-DTA. The phase compositions of powders were analyzed by XRD. The micrographs of the samples were investigated by SEM and the luminescent properties were researched by optical spectrum. The effects of H3BO3 on the phase composition and microstructure of the calcined powders were investigated. The results indicated that H3BO3 accelerated the formation of SrAl2O4 by consuming the intermediate phase. The addition of Dy2O3 stimulated the afterglow property due to the increase in the depth of the trap center in the materials.