Using the method of time domain and frequency domain dielectric spectrum, the response signals of applied field for grains, intergranuhr boundary layer, and barrier layer in a ceramics may be dissociated. So as to give the contribution of each mechanism in total resistance and total reactance of a sample. The effect of conductivity relaxation due to hopping conductance of polaron has been observed. This effect makes the impedance of the sample appear with inductance character. The properties of intergranular boundary in three kinds of typical ceramics of zinc oxide, strontium titanate, and barium titanate are compared.