Al2O3-Y2O3-ZrO2 ternary composite ceramics are synthesized via the traditional solid state reaction method and sintered at 14001500 ℃. The phase structure, the microstructure and the electrical properties of these samples are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and dielectric spectra. There are not any other impurity phases in this ternary system supported by XRD patterns, and additions of Y2O3 and ZrO2 into Al2O3 make contributions to the lower calcining heat. SEM indicates that the grain sizes of these samples are about 200500 nm. Furthermore, the densities are improved and the grain boundaries are clearer for the samples sintered at higher temperatures. Relaxation peaks are observed in the dielectric loss plots and the relaxation is of non-Debye type according to Cole-Cole complex impedance spectrum.