Abstract: There are 11 mud-rock flow channels in the reservoir of a hydropower station in the middle of the Yarlung Zangbo River. Frequency of the occurrence of debris flow is low. This paper comprehensively analyzes the effect of mud-rock flow in the dam site on project mainly through analyzing the fatalness of each mud-rock flow in the reservoir, the possibility of blocking up and the impact on hydropower station job projection. Among these channels, three channels are near the dam site and have great influence on waterwork in the dam site and construction safety. The results indicate the debris flow activities in the study area will not result in blocking of the main channel that possibly brings about flood in the down stream of the river.