The impedance spectra of amorphous Lithium ionic conductor 29.6P2O5-44.4Li2O-26.0LiCl and 36.3P3O5-44.4Li2O-15.1LiCl-4.2Al2O3 were studied. The equivalent circuit of the measuring box system and the dispersion relation of the interface impedance were given. Under a certain condition, this interface impendance can be transferred to the constant phase angle (CPA) impedance.