Abstract: The terrain and topographical characteristics loosening solid matter characteristics and rainfall characteristics as well as statics and dynamic characteristics of giant debris flow were obtained by field investigation and analysis on the debris flow hydrodynamic force conditions based on platform of ArcGIS and using DEM.The results show that the terrain and topographical can provide favorable condition for formation and running of runoff.The amount of loosening solid matter is so great that amplify dam.The severe local weather process with heavy precipitation short duration is the main cause for this massive mudslide.The bulk density of debris flow is 2.10 t/m³,is high density viscous debris flows,and yield stress is over 8 000Pa,the velocity of dayanyu xiaoyanyu(rainfall confluence area) and sanyanyu(debris flow accumulation area) is respectively 8.97 m/s,7.06 m/s,6.02 m/s,the maximum flow is 1 659 m³/s,1 553 m³/s,1 896 m³/s,the impact force is 46 676 tf,40 236 tf and 21 182 tf,so the destructive power is great and its damage is serious.The great destructive of debris flow in circulation terrain is mainly down cutting erosion,affected by the terrain,the impact force is decreased and the debris flow stacked.