Abstract: The minimum pressure along the upper flat pipe section of a pumped-storage power station is a critical controlling parameter for ensuring the safety of the water conveyance pipelines and the stable operation of the units. A mathematical model for transient flow analysis of the water conveyance and power generation system in pumped-storage power stations, incorporating Sobol global sensitivity analysis, was established. The study systematically investigated whether to set up an upstream surge chamber, and the effects of the inflow/outflow flow coefficient, throttled orifice diameter, and surge chamber diameter on the minimum pressure at two controlling sections along the upper flat pipe segment. The sensitivity of each parameter was quantitatively analyzed using the Sobol method. The findings indicate that, considering the installation of an upstream surge chamber, appropriately increasing the inflow/outflow coefficient with optimization, throttled orifice diameter, and surge chamber diameter can help mitigate the minimum internal water pressure at the upper flat pipe sections. The flow variation rate is one of the key factors affecting the minimum pressure at the upper flat pipe sections. The study quantitatively reveals the independent effect of parameter changes on the minimum pressure and the interaction effects among parameters, with the minimum pressure most significantly influenced by the throttled orifice diameter, followed by the surge chamber diameter and the inflow/outflow coefficient. The achieved results provide important technical support for the quantitative evaluation and optimization decision-making of water conveyance pipeline layout parameters.