Abstract: Catastrophic geo-hazards have occurred frequently in the karst areas of Southwestern China for these years because of internal, external geologic processes and human engineering activities, which makes it urgently necessary to reveal their triggering mechanisms for their consequences controlling. Detailed site geological investigation, full-scale block distinct-element-code modeling and related engineering geological analysis were conducted to recognize main characteristics, controlling factors and dynamic formation mechanism of a so-called underground mining-induced landslide. Results on the Pusa landslide show its dynamic formation is influenced by micro-landform, rock strata types, rock mass structure, weathering, goaf, heavy rainfall and, especially blasting vibration during underground developing and mining, i.e. controlling factor. Based on the numerical modeling, whole subsidence and clock-wise rotation are obvious characteristics of deformation caused by the goaf and the heavy rainfall during pre-failure of the landslide. What’s more, the whole subsidence which was caused by the goaf is one of the key characteristics of the underground mining-induced landslide. After the landslide behaves its critical failure, following dynamic responses include shattering, scraping off part top of the bed, debris flowing and final depositing. Finally, the dynamic formation mechanism is proposed based on evolution of main forces contributing the Pusa landslide. The forces are actuated by the seepage stress, vertical and horizontal blasting stresses, shear stress, unloading stress and dilation stress caused by the caved rock mass.