Abstract: In order to find out the causes of the landslide on the east side of the surface plant of Halagou coal mine, the geological conditions, seepage, and deformation characteristics of the landslide were investigated by means of on-site geological survey, hydrogeological drilling and surface displacement monitoring, and the mechanical mechanism of the landslide was analyzed by a numerical simulation method. The results show that a nearly EW-oriented paleogully is developed at the bottom of the Quaternary loose layer on the east of the landslide with two branches in the upstream. The surface water of Shendong Lake and the daily ecological irrigation water supplies the paleogully basin in large quantities, resulting in a rise of groundwater level and the formation of a discharge area at the foot of the landslide slope; Due to the leakage of a large amount of surface water, the groundwater seepage velocity increases, the water level rises, and the pore water pressure increases, and therefore the matrix suction decreases and the shear strength of the landslide soil decreases, resulting in the reduction of the anti-sliding force. A large amount of water seepage at the slope increases the weight of the slope and generates downward osmotic pressure, resulting in the increase of sliding force. And therefore, the landslide was induced. As the water temperature increases, the landslide stability coefficient decreases. Three drainage wells were constructed at the foot of the slope. After pumping, the groundwater level of the slope was reduced, and the leakage point of the upper ditch was treated. At present, the deformation of the landslide has been effectively controlled.