A brief description is given to the currente status of the study on slope rochmass deformability and FLAC-3D soft mare firstly and then
using FLAC-3D
deformation of Gapa landslide is studied by means of numerical simulation under natural situation and impounding conditions. On the basis of calculation results obtained from simulation
by means of analysis of displacement value of character ristic points in the main section and displacement vector
deformation features under natural situation and different impounding conditions are given . The relation of deformation features and stability of landslide is established . Finally
essential theory is given to evaluate stability of Gapa landslide in the future.