Abstract：The west route of South-to-North Water Transfer Project China lies in the east of Qinghai—Tibet Plateau. This area belongs to mountain-hazard-prone area due to the natural conditions of the special geology，landform，soil，vegetation，weather，hydrology and so on. Collapse，landslide，debris flow and other mountainous hazards are well developed，which are influenced and controlled by the natural factors and human activities. The main mountainous hazards are landslide，collapse，debris flow，dangerous slope，large-scale deposit. The secondary hazards are mountain torrents，water loss and soil erosion，freezing and thawing solifluction，road foundation collapse and so on. The distribution characteristics，rules and the status of other mountainous hazards are found out in west route of South-to-North Water Transfer Project through field survey，topography map implement，GPS fixed-point，aerial photos and TM，SPOT satellite image interpretation. The bursting scales of debris flow (the maximal flow，the total amount of a debris flow) are analyzed and predicted. The blockage of the river by debris flow (possible height，backwater length) and the quantitative analysis methods of the second possible hazards derived from debris flow are discussed. On the basis of the analysis，the possible influence of the mountainous hazards on the west route of South-to-North Water Transfer Project is considered；and the probable dangers are presented.
