The correlation of polarization with AC conductivity behavior of polycrystalline non-ferroelectric ceramics is more satisfied to be interpreted by three zones indicated in permittivity and AC conductivity spectra. These three zones concerning the dielectric and conductivity processes governing the response to an AC field have been identified in terms of the cluster model within the framework of percolation theory. Colossal dielectric permittivity of non-ferroelectric materials can be attributed to hopping polarization aligned via developing percolation clusters with high electron concentrations. The physical origin of the correlation between dielectric permittivity and AC conductivity of polycrystalline ceramics with respect to the effect of grain boundary has been clarified.