Abstract: Air and water permeabilities, suction, evolution properties of pore water pressure and pore air pressure in unsaturated compacted soil are studied over wide ranges of soil moisture and soil density by various improved instruments, i.e., a special triaxial apparatus developed by the authors, a set of facility of air permeability and a set of equipment of water infiltration characterized by measuring water content with gamma rays. Ralationship among suction, degree of saturation and denstity of the soil is established by several methods. Series of realistic methods for testing the engineering properties of unsaterated soils are summarized.