Abstract：For complexity and diversity of unsaturated soil behaviors，there lies a great difference in permeability characteristics between unsaturated soil and saturated soil. It is difficult to perform test of unsaturated soil because of many factors. With the special triaxial instrument of unsaturated soil，the permeability characteristics of unsaturated soil of the dyke of Yellow River are tested and studied，which sets up a basis for direct measuring the coefficient of hydraulic conductivity of unsaturated soil. According to the test results，the relation and changing law between confining pressure and permeability coefficient in different water content，and the relation and changing law of water content and permeability coefficient under different confining pressure are obtained. The relation curves are fitted to deduce correspondent fitting functions.
