Abstract: The dump,with the compact rock platform and high steep loose slope,which is formed during coal mining,is the most serious area of soil erosion in a surface coal mine.The confluence of compact platform is the main driving force for the erosion of slope in the dump,and the ground fissures at the front edge of the platform provide a preferential path for surface runoff to flow into the dump.These greatly increase the possibility of soil and water loss disasters such as collapse,landslide,and debris flow in the dump.Studying the mechanism of rainfall and micro-topography on the soil erosion of platform-slope system of dump can provide a scientific basis for the prevention and control of soil erosion in a surface coal mine dump.Taking the south dump of the Shengli Dong No.2 open-pit coal mine of Datang international power generation company in Xilinhot City,Xilingol League,Inner Mongolia as the research object,establishing an indoor model using similarity simulation principle and equivalent model of ground fissures,the evolution process of soil erosion,runoff and sediment yield characteristics and morphological characteristics of erosion ditch under different rainfall intensities(90,120,150 mm/h) and ground fissure depths (5,10,15,20 cm) were studied using simulated rainfall experiment.The results indicate that the soil erosion evolution process of platform-slope system of dump was divided into six stages:soil splash erosion and surface erosion,water filling and collapse of ground fissures,rill erosion,ground fissures through,slope shoulder collapse,and stable stage.The soil erosion process was the result of water erosion and gravity erosion.The runoff was 23.41,58.70,35.24 and 75.95 L with the ground fissure deep of 5,10,15 and 20 cm,and the corresponding erosion was 3.79,19.66,23.01 and 34.57 kg.The runoff and erosion increased with the increase of rainfall intensity.Mud flow was formed in the early stage of soil erosion process,and the sediment concentration was 1.03 kg/L under 90 mm/h rainfall intensity and 10 cm ground fissure depth.The runoff and erosion of platform-slope system of dump were the result of the joint action of ground fissure and rainfall intensity.The interactions of ground fissure and rainfall intensity have a significant relationship with runoff,and have an extremely significant relationship with erosion.The erosion with each period was 1.94-4.56,2.07-63.19,4.98-34.54,5.84-53.98,6.31-74.64 and 38.78-176.25 times of the control under different rainfall intensities and ground fissure depths,and the erosion presented continuously multi-peak multi-valleys.With the increase of rainfall intensity and ground fissure depth,the number of erosion gullies decreased,their length,width and depth increased,and the head cut erosion became more serious.