Abstract: Due to the exploitation of coal resources under the reservoir, the reservoir dam had collapsed and deformed to varying degrees, which posed a threat to the dam safety. Firstly, the hydrology and engineering geology were analyzed in Chengnan Reservoir project area, the mining situation was introduced on underground working face, the predicted parameters of probability integral method were determined, and the displacement and deformation of dam mining were predicted. Finally, ac cording to the forecasting results, under the condition of considering the influence of environment and water quality, a specific dam risk removal engineering measure w as formulated, the dam body was heightened and strengthened, and slope protection, retaining walls, toothed walls and roads were constructed according to different s ubsidence levels.