Sediment deposition caused by debris flows is an important process controlling the evolution and regression of lake, and even a pervasive environmental problem. The frequent debris flows construct a vital links between mountain slope and Qiong Lake transporting lots of sediment into lake, and further making the lake depth and lake area shallower and smaller constantly. In the paper, we select the Guanba River in the northeast of Qiong Lake as a case studying the effect of debris flows on Lake depositon and the characteristics of typical debris flow, and document the sediment deposition in the Guanba River estuary. The control factors contributing to debris flow initiation indicate that the debris flows are drove by rainfall, earthquake and human activities together, and the occurrence frequency of debris flows in the study area will continue to increase.