Abstract: The global stability is an important aspect in design and construction of arch dams. The global stability of dams is a three-dimensional nonlinear problem which involves heterogeneity, porous media, irreversible damage evolution. The nonlinear finite element method and geomechanical model tests are the main means to study the global stability of arch dams. Numerical simulation by a nonlinear finite element method (TFINE code) and a geomechanical model test with scale of 200∶1 are introduced. The displacement and stress distribution rules, failure mechanism and global stability of dams are explored according to the simulations and tests respectively. Both results are in good agreement. The global stability of the dams is evaluated synthetically by combining the results, the relatively weak site of abutment rock mass is provided, and some advises are proposed.