Abstract: Affected by complex topography and hydrogeological conditions, the problems of water damage in the underground mining process of Yanshanshan iron mine are particularly prominent.The special topographic features determine that the open pit is the point of convergence of surface water.If the surface water cannot be treated effectively, the surface water from the surrounding mountain will be taken into the open pit and infiltrated into the underground stope through the pit, causing serious water damage.In order to reduce the risk of water damage in underground mining and ensure production safety, this paper studies the surface water runoff law under the influence of iron ore mining based on the hydrogeological characteristics of Yanqianshan mining area, predicts the surface water runoff, and calculates the normal daily water volume and the maximum daily water volume at the bottom of the open pit.Moreover, this paper determines the boundary of surface subsidence area during the mining process by using numerical simulation method, optimizes the surface water drainage method in the mining area, proposes effective surface water control measures, and provides the basis for the surface water control and the open pit waterproof engineering design.