[Objective] A landslide occurred at Dingdong Primary School which is located in the southeast area of Guiding County in Guizhou Province. The canteen, accommodation, the ground floor and wall of Dingdong Primary School were cracked. The landslide is a direct threat to the safety of school building, the nearby houses and road, so it is necessary to find out the mechanism of its occurrence, and to provide a scientific basis for landslide treatment.[Methods] The methods such as drilling, well, high density resistivity were used to investigate the structure and deformation characteristics of the landslide, combining with geological and environmental conditions, and the formation mechanism of the landslide are studied. At the same time, the stress-strain field and deformation failure features of the landslide is analyzed by means of Adina software under conditions of the nature and rainstorm.[Results] The artificial fill and rainfall is the main reason for the formation of the landslide and the landslide failure mode belongs to creep-crack type. The special topography and low compaction degree filling is internal cause of landslide, and longtime rainfall infiltration is external cause.[Conclusion] Unreasonable artificial fill is the direct reason of the landslide, and landslide could slide along the interface between filling and clay layer.