Abstract: Landslide dammed lake is a common geological disaster in mountainous area,which may bring great loss to life and property of the people in downstream area after its breaching.Focus on the process of forming,disaster-pregnant and disaster-causing,the formation mechanism and simulation method of the disaster chain for dammed lake were studied.Based on the formation process of landslide dammed lake and the grain size distribution characteristics of landslide dam,a rapid evaluation method for the stability of landslide dam was established.Further,the erosion characteristics and breach process of landslide dam were summarized,then a numerical simulation method for the breach process of landslide dammed lake was proposed.Based on the formation and breach mechanisms of landslide dammed lake and considering the morphology,particle composition,erosion characteristics of landslide dam and the hydrodynamic conditions of dammed lake,the disaster chain simulation method was a scientific and efficient tool to analyze the landslide dam stability,the flood hydrograph and the breaching evolution rule.Three typical landslide dammed lake cases in the 21st Century in China was used to testify the rationality of simulation method,which proved that the simulation method can provide a reference for the risk assessment.