Abstract: Dielectric measurement was carried out on D354 anion-exchange beads dispersed in KCl solutions with different concentrations. Distinct dielectric relaxations were observed in the frequency between 106 Hz and 107 Hz, and particular relations between permittivity, electric conductivity, relaxation time and the solution concentration were obtained. It was proved that such a relaxation is a non-single mechanism relaxation that due mainly to interfacial polarization, then the particular dielectric behavior was interpreted by the theory of Maxwell-Wagner and properties of electrical double layer, and the information of ion transformation and accumulation at the interface between the particles and solution phase in the presence of an external AC (alternative current) field was obtained. It is conclude that, the electric double layer that formed during the static ionic equilibrium would not be destroyed by added AC field; the enrichment of counterions in electric double layer predicts dielectric increment, while the thickness of electric double layer decides the magnitude of the relaxation frequency; and the ionic strength in electric double layer was fond corresponding to the ionic strength of pure KCl solution with a concentration of 0.7 mmol•L－1.