Abstract: The apparatus was applied to determine the parameter of unsaturated soils in the laboratory,based on the characteristics of soil that the ability of adsorption was invariable in the steady seepage state,which could test the water-soil characteristic curve in and the conductivity of unsaturated soils the process of desorption and sorption.Under the same conditions,the water-soil characteristic curve attained from the steady seepage test accorded with the result obtained from the 1250 volumetric pressure plate extractor made in Soilmoisture Equipment Corp of USA.The experimental results indicate that the apparatus is stable,and can be used in the laboratory to study soils.