Abstract: The debris flow happened on 8th august 2010 in Zhouqu county is a disaster which caused the biggest damage in Chinese recorded history.It is extremely meaningful to faithfully record the features,forming reasons and triggering factors of this debris flow,analysis the developments and propose the risk mitigation measures for the reconstructions guidance and further study of this disaster.This paper takes the debris flow at Luojiayu gulley as an example.Based on detailed exploration,the forming reasons of this debris flow was analyzed from the geological environmental point of view.The zoning and deposition characteristics of this debris flow were described.The development features of the debris flow was analyzed according to the accumulation features,values of unit weights,velocity and discharge.The forming reasons were studied based on the topography,solid material properties,and the extremely rainfall conditions.