To decide the process and factors affected runoff and the characteristic of water erosion of large dump which produced during construction of railway engineering,study of natural rainfall for Hezhuang Dump in Beitongpu railway rebuilding project is made during raining season.The runoff and sediment yield is affected by the process of rainfall and the function of water and soil conservation measurement.The characteristic of top soil will changed by splash erosion and surface erosion,accordingly to alert the route of runoff and seepage and work to unconsistenty of soil erosion.The region of flow produce is loose embankment and the flat roof,the gully erosion chain is the main cause of the sediment yield increase.