Abstract: Pumped storage units primarily undertake peak shaving and valley filling, energy storage, frequency and phase modulation, and emergency standby for the power grid, serving as core regulators to support the large-scale grid integration and consumption of new energy. To ensure the dynamic stability of the upper frame-stator base system of a large pumped storage unit, this paper calculates its first six natural frequencies using the finite element method and compares them with common excitation frequencies of the unit to guarantee long-term safe and stable operation. The natural frequencies of the upper frame-stator base system under different structural configurations with elastic dampers, with tangential supports, and without any supports are compared. The results indicate that elastic dampers can significantly increase the horizontal vibration frequency of the upper frame by 413%, while tangential support devices can significantly increase the torsional vibration frequency by 74%.