Abstract: A hydropower station project is built on high mountain canyon tracts of which natural slope usually has a zestier of strong unloading rock and a zestier of ebb unloading and corresponding zone of strong (or ebb) weathering rock, and intact fresh rock in its inside. But there is a series of sheeted fracture or zone of fracture named as deep fracture. There are two deformable bodies on the right bank of the Pubugou hydropower station reservoir. This paper analyzes mechanisms of deep frctures and characteristics of deformation based on field investigation of the distribution characterization and deformation behavior. It is concluded that the deep fracture was caused by epigenetic reformation by release of high geostatic stresses. The formation age of the deep fracture is when the river changes from wide valley to canyon by stream trenching.