The soil-water characteristic curves are used to investigate the fundamental behaviors of unsaturated soils such as pore size distribution, permeability, and strength. In order to suggest a generalized procedure to estimate the soil-water characteristic curves of natural soils, a new pressure cell extractor was developed for deformable soils and experimental tests were carried out on the specimens of various void ratios. During experimental tests, the residual soils used in this study showed a significant volume change due to matric suction. The results highlight the importance of correction for volume change. The normalized constituent parameters of soil-water characteristic curves exhibit a linear relationship with the normalized void ratio, indicating the validity of the reference state approach in estimating the soil-water characteristic curves of natural soils. An empirical procedure was provided for the estimation of generalized soil-water characteristic curves using liquid limit state as a reference state.