Abstract: Rainfall is the main driving factor for runoff sorting in surface moraine areas. Taking the surface moraine particles of Shangri-La Pulang Copper Mine as the research object，the indoor artificial simulated rainfall test method was used to study the separation law of moraine runoff under different rainfall intensities under the condition of runoff slope of 32°. The results show that the moraine particles have significant sorting effect under different rainfall intensity runoff scouring，and the particle size of moraine runoff scouring increases with the increase of rainfall intensity. With the increase of rainfall intensity，the number of erosion gullies on moraine slope increases，and the area and depth of erosion gullies also increase accordingly. The more serious the erosion of slope runoff，the weaker the selectivity of runoff sorting to particle size. The research results can formulate effective measures for the prevention and control of the runoff separation of moraine particles，and avoid the finegrained moraine particles after runoff separation into the scope of mining activities，which is of great significance for the prevention and control of underground debris flow disasters in mines.

Key words: moraine particles, rainfall intensity, runoff erosion, sorting