The triaxial test instrument for unsaturated soils controlled by stress and strain was used to measure the matric suction and volumetric water content of unsaturated soils; and a set of soil-water characteristic curves of silty clay were obtained. The equation of soil-water characteristic curve was also gained by use of nonlinear curve fitting. The concrete form of the Mualem equation was deduced based on the relation between the soil-water characteristic curve equation and the permeability function equation. The results calculated by the concrete form of the Mualem equation are consistent with those measured by the direct method. The concrete form of the Mualem equation was further proved to be reasonable.