Abstract:High in-situ stress and low rock mass strength are the main characteristics of underground powerhouse of JinpingⅠhydropower station, surrounding rock stability problem is prominent during construction period. Combining with engineering geological mechanics method and three-dimensional finite element method, the construction process of underground powerhouse was simulated, discussed the stress and deformation of surrounding rock, stability characteristics and main influence factors of surrounding rock stability. The calculation results indicate that the stress and deformation and stability characteristics were obviously effected by fault, cavity arrangement and excavation procedure. During the excavation procedure, the maximum stress part is constantly changing, stress and deformation of surrounding rock are also continuously increasing, especially the deformation of the side wall. At grotto's intersection and fault location, deformation is large, plastic zone is basically connected; strengthened supporting measures should be taken to ensure the stability of surrounding rock.