Abstract: This paper studies a landslide at a large coal mine site in Shanxi province. The effect of underground mining on the stability of the old landslide and the reactivation mechanism are analyzed. The mining displacement can greatly reduce the strength of the soil. The tensile cracks can provide infiltration path for surface water which can reduce the physical and mechanical properties of the soil of sliding zone. The gob movement and deformation in the front of landslide play a dragging role in the damage of the landslide. The boundaries and the sliding surface of the landslide have been determined by the ways of engineering geological mapping, drilling, geophysical investigation and deformation monitoring. The landslide is zoned based on the topography, material composition and deformation characters. The mitigation measures of ordered retaining structures in the landslide and anti-sliding pillar in the mine have been carried out according to the deformation characteristics, geological and environmental conditions and mining demand. Monitoring data show that the landslide keeps stable as the mitigation measure putting into effect.