To obtain Al2O3-based low-temperature co-fired ceramic (LTCC) materials with low dielectric loss and high breakdown strength, glass/ceramics of x(La2O3-CaO-B2O3-SiO2)(LCBS)+(1-x)Al2O3 were synthesized by a solid-state method. The structure and properties of the sintered samples were characterized by X-ray diffractometer, scanning electron microscope, vector network analyzer, high voltage breakdown instrument, and high-temperature dielectric spectrometer. The results show that adding an appropriate amount of LCBS glass powder can increase the density, reduce the dielectric loss and improve the breakdown strength of the composites. Moreover, based on the complex impedance spectrum analysis, the addition of LCBS can significantly increase the resistivity and activation energy of glass/ceramics. When Al2O3 ceramic with 44 %(mole fraction) LCBS glass (abbreviated G44) is sintered at 850 ℃ for 0.5 h, a LTCC ceramic material with the superior properties (i.e., εr=7.14, Q×f =5 769 GHz at f =13 GHz, and Eb=57.44 kV/mm) can be obtained.