Abstract: Based on site investigation and tests,it is found that Sanyanyu is a high-frequency debris flow gully with many catastrophic debris flow occurred in history.Debris flow deposits of different periods overlay each other.By comparing the remote sensing images before and after the debris flow and taking ArcGIS as an analyzing tool,it is found that "8.8" extremely big debris flow carries large amount of solids with a total volume of 152.18×10⁴m³,damaging buildings and blocking rivers.It forms 1.9km long narrow deposits with a volume of 110.58×10⁴m³ and the maximum accumulation thickness of 10.8m.For accumulation characteristics of debris flows are the objective records of the beginning and developing process of debris flows,this paper analyzes accumulation characteristics and destruction degrees in different parts of earlier debris flows and "8.8" debris flow.The results can be taken as references for comprehensive treatment and post-disaster reconstruction planning.