Abstract: The cavern group of an underground powerhouse of a pumping and storage power station has the characteristics of large scale, dense cavern, complex construction conditions, high side wall of the main cavern and large span. The stability of surrounding rock of underground powerhouse cavern group of a pumped storage power station under bolt-anchored conditions is analyzed by a numerical analysis method FLAC^3D which adopted the fast Lagrange difference analysis method is used to calculate the stability of surrounding rock of underground powerhouse cavern group of a pumped storage power station under the condition of no support and with support. The stress field before and after excavation and the distribution and variation of surrounding rock deformation under tunnel excavation and bolt anchoring conditions are systematically analyzed, which provides reference and basic data for stability evaluation and engineering design of underground powerhouse cavern group. The results are as follows. After excavation, the rock deformation around the cave generally develops towards the open side, the vault of the cave gradually sinks, and the floor rebounds. The supporting measures can effectively reduce the deformation of surrounding rock, the plastic zone of surrounding rock is significantly reduced, and the plastic yield degree is significantly reduced. Compared with before and after the support, the stress relaxation range is obviously reduced, and the support can obviously improve the minimum principal stress distribution of surrounding rock, and effectively support the surrounding rock to lift the arch, and improve the stability of surrounding rock.