The BaAl2Si2O8：Eu2+ blue phosphor was synthesized by one-step calcination of the precursor prepared by chemical coprecipitation. X-ray diffraction and fluorescence spectrophotometry were used to investigate the structural and luminescent properties of the BaAl2Si2O8：Eu2+ blue phosphor. The result showed the BaAl2Si2O8：Eu2+ synthesized by the process was pure. The excitation spectrum of the BaAl2Si2O8：Eu2+ blue phosphor extended from 240 to 410 nm， and the peak appeared around 320 nm，thus the phosphor can be excited effectively by InGaN chip in the range of 350—410 nm. The emission spectrum excited by 365 nm showed a characteristic wide band with the peak at about 465 nm. The emission spectrum intensity firstly increased with Eu2+ doping concentration increasing，then decreased. The strongest emission intensity was obtained when Eu2+ doping concentration reached 3.5mol%. The concentration quenching mechanism was caused by the exchange interaction of Eu2+ ions according to the Dexter theory.