Abstract: The non−pillar sublevel caving method is often used in the black metal mines with open−pit to underground, which can easily cause instability of open−pit slopes and threaten the safety of surrounding buildings in the mining area. Taking the Lijiahe Iron Mine with steep surface slopes and strong terrain cutting as the research object, a detailed numerical model was constructed based on the surface aerial point cloud data and the production plans. The numerical simulation was used to study the surface rock movement characteristics of open−pit pits under the action of continuous underground mining disturbance. In combination with the factors such as terrain, vegetation, crops, and roads, a feasible surface waste rock filling scheme was compared and selected. The results showed that the No.1 mine pit showed local sporadic damage, while the No.2 mine pit was mainly damaged in the north−eastern area under the deep mining and the terrain and distribution of the ore body. The overall surface subsidence stability of the No.1 mine pit was better than that of the No.2 mine pit. Finally, a surface waste rock filling scheme was selected that moves from the sidewall to the centre and then northwards.