Today the main part of energy is produced by hydropower stations, which based on existing conditions they can be either surface or underground method. It is essential to be created large-scale structures for underground power stations, due to high sensitivity, durability and large size of these structures, design and stability analysis is very important. Stability analysis and sustainability issues of underground spaces are one of the practical and common issues in rock mechanic and geotechnical studies. Considering the development of numerous softwares and the advent of advanced and suitable computers for repetitive calculations, numerical methods of stability analysis of underground structures are widely used in the design and excavation stages. Accordingly three-dimensional softwares that works based on numerical methods can be used in the design and stability analysis and estimating the support system of underground spaces. In this study, stability of Bakhteyari cavern has been investigated in both term of the static and the dynamic behaviour. First, the static analysis was considered on the model, and by observing the instability, according to experimental methods, the support system was designed for it. Subsequently, after static equilibrium, dynamic analysis of the model was accomplished. For this purpose, scaling of the spectrum of earthquake was done, and with the same supporting system, which used in static analysis, was exerted to the model. Then the stability conditions were investigated in dynamic mode. By observing the instability, the support system was changed and the dynamic equilibrium was investigated in new conditions.