In order to study the unit ' s movement law ， in this paper,according to the theory of random vibration ,the calculating model is established, and the response spectrum method and advanced testing technology are used in testing and calculation of large hydro-electric generating sets. The results show that the vibration energy is mainly concentrated in the vicinity of the fundamental frequency, and random vibration of the water load is mainly low-frequency vibration,which affects the vibration of the turbine significantly, but has little affect on the other parts of the shaft. The calculated results agree well with the measured data, which shows the correctness of the theory analysis.