A series of long persistent phosphors Sr1-3x Al2O4 : Eu2+xDy3+2x (X=0.005, 0.010, 0.015, 0.020, 0.025)were prepared through a combustion method at 600oC. We found that all the series of samples have good long afterglow properties by the naked eye. Then we use the laser to stimulate phosphors at 325nm, and their emission spectrums were tested by a spectrograph. We can found that the emission peaks of all samples are all results from the 4f65d 4f7 (8S7/2) transition of Eu2+ instead of the 4f7 (6P7/2) 4f7 (8S7/2) transition of Eu2+ ions. In addition, the afterglow characteristic of the various samples and the same sample at different wavelengths was investigated. Our results show that each decay curve consists of a rapid decay part followed by a long slow one and all samples have the same afterglow mechanism.