Abstract: The Manla Hydro-Junction Project in Tibet is located on the high plateau area with high earthquake intensity. There are large-scale landslides existing within up-and down-streams near the hydro-Junction site on the left bank,which have a potential threat to the project.Therefore,a special investigation and an experimental test has been done on the landslides on left bank and a deformation monitoring network has been set up and covered the landslides. The deformation data were collected during the reservoir construction and imponding and early operation stage of the project. Analysis of the deformation data permitted us to predict the possible slip of the landslides. The reuslt is very important for the safety of the Manla Hydro-Junction.