Shanxi Xinyuan Coal Corporation Ltd. is a permo-carboniferous coal field in north China, the main coal seams are 3 , 9 , 15  coal, most of the areas are ordovician water pressure mining area. Previous exploration and excavation activities have revealed that the Fengfeng and Majiagou formations of the ordovician system in well-field system have different water level and water-rich characteristics, and there are local water-rich abnormal areas of the limestone of the Taiyuan formation, which threaten the safety of the mine to varying degrees. Obviously, the general evaluation based on the water inrush coefficient method can not objectively reflect the influence degree of each layer on the coal seam. This paper takes the No. 9 Coal Seam in new well-field system as an example to discuss the risk evaluation method of karst water inrush in the coal seam floor It provides a more reliable basis for mine water control work.