The invention discloses a soil pillar seepage erosion experiment device under rainwater infiltration and a soil-water separation experiment scheme. The soil pillar seepage erosion experiment device under the rainwater infiltration comprises an experiment device bracket, an upstream water head control system, a rigid wall seepage chamber and an erosion mixed fluid collection system, wherein the experiment device bracket comprises a bottom plate with adjustable height, a top plate and a middle movable plate; the upstream water head control system is used for controlling rainfall intensity borneby a soil pillar and monitoring hydraulic gradient borne by the soil pillar; the rigid wall seepage chamber is a core part and is used for containing a soil pillar test sample to finish a seepage erosion process; the erosion mixed fluid collection system is used for collecting erosion mixed fluid in a collection phase; the soil-water separation experiment scheme comprises the steps of detecting clay particle concentration in the erosion mixed fluid, the quality of sand and gravel mixed particles and the quality of erosion fluid. The soil pillar seepage erosion experiment device under the rainwater infiltration and the soil-water separation experiment scheme can be used for effectively realizing inner erosion experiment and analysis under a rainwater infiltration condition.