The luminescent intensity of Li2CaSiO4:1% Dy3 + at 250 ℃ was 62% of that at room temperature. It was found that the NH4F flux could not only enhance the luminescence intensity but also improve the temperature stability of Li2CaSiO4:1%Dy3+ to 85% of room temperature at 250 ℃. The mechanism of NH4F flux was discussed by means of measures of infrared spectrum (FITR), scanning electron microscope (SEM), decay lifetime and photoluminescence (PL).