Eu2+, Dy3+ co-doped strontium aluminate (SrAl2O4) phosphor nanometer powders with high brightness and long afterglow were prepared by heating the precursor gel (resulted from sol-gel method) at 900℃ and a reductive atmosphere of active carbon. The average particle size of the SrAl2O4:Eu, Dy phosphor powders was 59±7nm and its optical properties have been studied systematically. The broad band UV excited luminescence of the SrAl2O4: Eu, Dy was observed at λmax=506nm due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ ion. The results indicated that the main peaks in the emission and excitation spectrum shifted to the short wavelength compared with phosphor obtained by the solid-state reaction synthesis method. The decay speed of the afterglow for nanometer phosphors was faster than that obtained by the solid-state reaction method.