Abstract: The typical subgrade slope of Chengdu-Chongqing railway is made of sandstone-mudstone layers and its weathering zones are covered by a sand layerwith a thickness of 2~5 m. Simulation tests indicate that the hydraulic and mechanical responses of the slope to a rainfall process is influenced by the initial permeability of the sand layer, the rainfall style and the rainfall amount. The rainfall process which can have a remarkable influence on the seepage field and stress field of the slope should satisfy the following requirements simultaneously: (1) due to a long time of hot weather before rain, the soil layer is intensely evaporated and its initial permeability is good; (2) the rainfall process begins with a moderate or a heavy rain, and continues for a longtime; and (3) the rainfall lasts a longtime, and the rainfall amount is great.