With the method of fractal model to forecast the soil-water characteristics of unsaturated soil,it studies the process of unsaturated soil seepage under rainfall infiltration and evaporation related to climatic changes. Owing to the evaporation,the negative pore-water pressure increases gradually in the superficial layer of clayey soil slopes. The soils at the toe of the slope reach the saturated state at first while the retardation phenomenon occurs both at the surface and top of clayey soil slope. During the process of infiltration,positive pore-water pressure can be hardly generated at the toes of silt and sand slopes. The infiltration on the surface of clayey soil slope is small,and it is controlled by factors such as initial water content,rainfall type,hydraulic conductivity,etc. The rate of actual evaporation (AE) is only equal to the potential evaporation (PE) rate when the soil is saturated. The ratio AE / PE is the function of the suction.