Abstract: This paper is based on the SWCC obtained from the test with the triaxial test instrument for unsaturated soils controlled by stress and strain(WF)in the laboratory.The test results show that the SWCCs of two kind of soils are different greatly.The state of the soil in the foundation under the reservoir changes form nature state to unsaturated state,and further to saturated state,because of the increase of water content after sluice of the reservoir.The change course of soil saturation is analysed with FEM for seepage of unsteady and unsaturated conditions.The laboratory test results are further used in the numerical analysis.The engineering geology is influenced greatly by the change course.It is found that the provision of cut seepage ditch can diminish the influence of the change course.From the analysis,the effect of the measure of seepage control can reduce the groundwater level and reduce the water content of the soils up the groundwater level.This is important to reduce immerge and salt-basify for the project.