The effect of NH4Cl flux on the crystal structure, morphology, luminous intensity and the Commission International del＇Eclairage （CIE）chromaticity coordinates of Li2SrSiO4： 1%Dy3＋ was discussed, and the mechanism of action of NH4Clflux was presented. The results indicated that the reaction process in the synthesis of Li2SrSiO4： 1% Dy3＋ could be changed due to the formation of proper fluid phase, and the purity phase with sphere-like grain and smooth surface was produced by using 2%NH,Cl. The luminous intensity of Li2SrSiO,： Dy3＋ was increased 110% by adding of 2%NH4Cl compared with that without NH4Cl, and the CIE chromaticity coordinates （0.262,0.293）moved toward the ideal white light coordinates.