Electroosmosis is an efficient process that can facilitate the dewatering of high-water content clays and the decontamination of soils. Addition of background electrolyte is commonly used particularly in electrokinetic remediation. However, some experiments indicate that electroosmotic drainage rates increase in electrolyte solutions with higher concentration, while others suggest that there is an optimal concentration, below or above which the dewatering flow gets slower. Besides, it is also found that the electroosmotic permeability can be taken as independent of electrolyte concentration. The classical Helmholtz–Smoluchowski model fails to explicit the relationship of electroosmotic permeability coefficient and electrolyte concentration. The recent ion migration model interpreted the optimal salt content of electroosmotic permeability, but in a qualitative way. To further clarify the influence of electrolyte concentration, electroosmotic tests were conducted with variable charge soil in series of initial NaCl concentrations. The results showed that the electroosmotic permeability reached a maximum value at NaCl concentration of 0.12 mol/L. The authors tried to substitute the cation current density and cation electro-migration with the apparent electric current and total electro-migration flux of cations and anions in ion migration model, for the purpose of easier accessibility of parameters required. It turned out that the calculated electroosmotic permeability coefficient was in better agreement with the experimental values.