Abstract: The distribution of moisture content in earth dams is an importent factor influencing the stress and stability of dams. In this paper the principles of moisture movement in uasaturated earth dam are first discussed. practical mathematical model and a numerical calculation method are developed for investigating the soil moisture content at various points in earth dams. Some illustrative computation examples are given. The results of this research show that the above mentioned calculation method is applicable to analyzing unsteady seepage flow problem of some unsaturated earth