According to the flood discharge characteristics of pumped-storage power plants, such as high head, low discharge, and static reservoir water, a 1∶25-scale physical model of a shaft spillway was established based on the shaft system consisting of a circular guide-pier weir, a horseshoe-shaped stilling shaft and a pressurized sloped section, and the flow characteristics of the circular guide-pier weir and the energy dissipation performance of the shaft system were investigated. The experimental results show that the comprehensive discharge coefficient of the circular guide-pier weir ranges from 0.4 to 0.5, effectively ensuring symmetrical flow entry into the shaft and forming detached-wall jets to eliminate wall cavitation risks and enhance air entrainment. The synergistic operation between the stilling shaft and the pressurized sloped section significantly improves energy dissipation efficiency and flow control performance. The horseshoe-shaped stilling shaft demonstrates superior energy dissipation performance and downstream flow regime stability.The energy dissipation rate of the shaft system exceeds 88%, and increases as the discharge decreases.