Abstract: A simple approach is proposed to quantify the effect of the initial void ratio on the relative coefficient of permeability for unsaturated soils based on the incremental relationship between the degree of saturation and the initial void ratio and the prediction of the permeability function for unsaturated soils by use of the soil-water characteristic curve (SWCC). For a given soil and the SWCC equation, only one additional parameter is introduced, which can be conveniently calibrated by the conventional SWCC tests. The relative coefficient of permeability for the same soil with different initial void ratios can be predicted by this approach. The proposed approach is validated through experimental data from the literatures in which both the SWCCs and the coefficients of permeability with different initial void ratios are measured.