A model to determine the electrical potential and ionic concentration distributions in the overlapped EDL fields between two infinitely large flat plates was developed in this paper. It was found that the treatment in the classical theory may lead to an inaccurate description due to the misuse of the Boltzmann equation. New governing equations for such an overlapped EDL field were derived, The potential distribution and ionic concentration distributions for inorganic oxide-aqueous solution systems were calculated. The results were compared with the predictions of the classical theory. Differences between our model and the classical treatment were found, especially at small separation distance.