Due to the complexity and variability of unsaturated soil, the permeability property of unsaturated soils is clearly different from that of saturated soil. And because the test equipment is more complex and technical requirements are higher and diachronic cycle is longer, the researches related are slow. Using the triaxial apparatus of unsaturated soil, the direct and indirect experiments to study the permeability coefficient of unsaturated silty clay are done. Test results show that the permeability coefficient of unsaturated soil can be done by the indirect method and direct method. Not only the direct measurements of the permeability coefficient of unsaturated soil are realized through this trial, but also the reliability of indirect method is proved.