Abstract: The foundation soil of large channels in northern Xinjiang is mostly white sandstone and mudstone, and its hydraulic characteristics determine the formation and development of channel structural diseases. To this end, the white sandstone and mudstone of Beitun Irrigation in Altay, Xinjiang are taken as the objects to test their physical mechanics and impermeability indexes. According to the theory of unsaturated soil, the soil-water characteristic curve is obtained by the filter paper method, and based on the Gardner, Van Genuchten and Fredlund & Xing models the parameters of the soil-water characteristic curve is filled and their water-retention characteristics are analyzed; combined with the soil-water characteristic curve. Combined with its soil-water characteristic curve, the Childs & Collis-Geroge model is used to study the unsaturated permeability curve. The results show that the white sandstone and mudstone are expansive and low-permeability soil. The white sandstone has high shear strength and low compressibility. The best fitting effect of the SWCC of white sandstone and mudstone are the GA model and VG model, respectively, and mudstone has better water-retention performance than the that white sandstone. The relative permeability coefficient decreases sharply with the increase of matrix suction. Within a certain range of matrix suction, they are linear curves in a double-logarithmic coordinate system.