PbOCaOB2O3SiO2 glass powder is the main component of low temperature cofired ceramics (LTCC) raw green tape with high overload resistance. The crystallization behavior of glass powder affects the sintering performance, and then determines the performance of substrate. The effect of Al2O3 content on crystallization behavior and sintering performance of PbOCaOB2O3SiO2 glass was studied. The results show that the addition of Al2O3 into PbOCaOB2O3SiO2 glass can reduce the trend of crystallization， prevent the precipitation of high expansion crystalline phase and improve the sintering density of glass. The crystallization peak temperature of PbOCaOB2O3SiO2 glass powder without Al2O3 is 862 ℃, and cristobalite phase precipitates during sintering, which makes the average coefficient of linear expansion reach 260.8×10-7 ℃-1 at 20~200 ℃. The addition of 2.1% (mass fraction) Al2O3 into PbOCaOB2O3SiO2 glass can significantly reduce the crystallization capability of glass, and the expansion coefficient decreases to 72.9×10-7 ℃-1 after sintering at 700 ℃, with significantly increased dielectric constant from 6.30 to 7.02.