| The glass-ceramic of SiO2Al2O3-MgO-La2O3 has been chosen as the basic system. And the transformation of the microwave dielectric properties for this kind of glass-ceramic has been researched by the method of adjusting the proportion of PbO and La2O3 as well as changing heat-treating. The crystallization, dielectric property and microcrystalline phase have been analysed by perturbation method combined the XRD and SEM.The result shows that: It's the crystal phase controlled the εr value of this system , but not certain element;the phase of PbB4O7 and Zn3(BO3)2 as well as La4Ti(Si2O7)2(TiO2)8 have high εr appropriate content of PbO make the τf approach zero, and the phase of La4Ti(Si2O7)2(TiO2)8 has minus τf;Q value bases on the degree of crystallization, and then controlled by microcrystalline phase.After replaced PbO by ZnO, the dielectric property became better. Different heat-treatment can change the crystal structure of this system.In the experiment, the glass-ceramics that have the excellent dielectric properties were achieved. For example, one sample (PbO, 8.8wt%, 850°C for 72hrs) has the dielectric properties: εr 13.675, Q = 2126.5, τf =9.8 ppm/°C, and another sample (ZnO14wt%, 600°C for 3hrs and then 850℃ for 40hrs) has the dielectric properties: εr= 16.528, Q=2754.8, εf = -30ppm/°C.
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