Abstract: To address the challenge of accurately obtaining accurate modal characteristics of a runner in its actual working state through field tests, a refined numerical model of the real runner of a reversible pumped storage unit in a domestic power station was developed.Pre-stress mode analysis and wet mode analysis were conducted under the influence of various fluid media and surrounding water bodies using fluid-structure interaction and acoustic-solid interaction methods, which compensates for the limitations of traditional numerical methods inadequately considering boundary conditions.The results indicate that pre-stress has minimal impact on the natural frequency of the runner.In contrast, the fluid additive mass effect significantly influences the bending vibration mode of the runner, while diminishing as the order increases.The drop-off ratio of the wet mode frequency of the runner is found to be between 0.5 and 0.8, while the tail water has negligible effects on the modal characteristics of the runner.These research findings provide crucial guidance for accurately predicting the modal characteristics of a runner, helping to prevent resonance between hydraulic excitation and the natural frequency of a runner from the design stage, thereby ensuring the safe and stable operation of power stations.