This paper is directed against the reality problem that it is very difficult to measure the critical speed of the shaft system in a large scale hydrogenerator unit in operating. 針對大型水輪發電機組軸系臨界轉速難以實際測定的現實問題,從理論分析的角度出發,抓住水力機組軸系結構的基本特點,提出采用較為簡單的模擬結構,試驗研究水力機組軸系固有頻率及其振型特征。