Abstract: According to the complicated geological conditions of steep coal seam, the No.5 seam in west fourth mining area of -410 m level in Muchengjian Mine was taken as research object, the discrete element numerical simulation method was used to simulate the mining process of steep flexible shield supports. The results show that the stress-strain of coal seam roof and floor and ventilation roadway showed significantly improved with the increasing of filling rate; the stress concentration region was decreased, which protected ventilation roadway from the influence of mining and improved the safety of backfill mining.