We establish a new ionic conductivity model based on the Nernst-Einstein equation in which the diffusion coefficient is derived from modified double lattice-nonrandom-Pitzer-Debye-Huckel (MDL-NR-PDH) model. The proposed model takes into account the mobility of the salt and the motion of the polymer host simultaneously by expressing the effective chemical potential as the sum of chemical potentials of the salt and the polymer. To describe the segmental motion of the polymer chain, which is the well-known conduction mechanism for solid polymer electrolyte (SPE) systems, the effective co-ordinated unit parameter is introduced. The obtained co-ordinated unit parameter for each state is used to describe the behavior of the ionic conductivities of the given systems. Good agreement is obtained upon comparison with experimental data of various PEO and salt systems in the interested ranges. (c) 2005 Elsevier Ltd. All rights reserved.