[Objective] Using Longdongshui landslide as a case, this article analyzed the genesis mechanism of this kind of landslide from the aspects of hydrostatic pressure and sliding belt softening, and aimed to provide theoretical basis for further identification and research of this kind of landslide.[Methods] Through detailed field geological survey, remote sensing camera, engineering geological mapping and analysis of discrete element numerical simulation, the characteristics of deformation and failure of the landslide were assessed, and the mechanism of the disaster was explored.[Results] The rolling syncline shape by geological structure formed the rudiment of the landslide; soft and hard interbedding structure provided the material basis for the landslide; three directional emptiness for landform condition provided space for the motion and deformation space; unloading and tectonic fracture provided precedent infiltration channel for surface water; water softening effect of the potential sliding surface by groundwater and static water pressure were the triggering factors of landslide.[Conclusion] The movement of the sliding body is not only the effect of the hydrostatic pressure of the posterior margin, but also is the physical softening of the groundwater. It is the joint effect of the hydrostatic pressure and the physical softening of the trailing edge fracture that will result to, and furthermore, the trailing edge hydrostatic pressure plays an accelerated role in the deformation and sliding of the slope.