Abstract: The vibration attenuation characteristics have a great influence on the dynamic behavior of the shaft system of hydro-generator units. In order to accurately describe the vibration characteristics of the shaft system of hydro-generator units under hydraulic excitation, this paper deems it necessary to investigate the vibration attenuation characteristics of the shaft system. Firstly, a method of extracting hydraulic excitation feature based on PSO-VMD is proposed to analyze the vibration characteristics of hydraulic excitation. Then, the vibration transmission models with no bearing shaft unit and the vibration transmission model with no bearing shaft unit are established by wave finite element method. According to the models, the vibration transmission equation of the shaft system of the hydro-generator units is constructed by wave finite element method. And according to the constructed vibration transmission equations of the shaft system, the calculation method of the vibration attenuation coefficient of the shaft system is determined. Finally, the vibration attenuation characteristics of the shaft system are analyzed by an example. The research findings show that the vibration transmission model and vibration attenuation coefficient calculation method of shaft system of hydro-generator units proposed in this paper are feasible and effective, which provides a certain theoretical basis for further in-depth research on the influence of vibration attenuation characteristics on the dynamic behavior of shaft system of hydro-generator units.