The severe vibration of a hydropower plant under large load condition with partial water head has been existed since the unit put into operation. In this paper

the method of extracting the specific frequency component is used to find out that the frequency component of 25 ～ 35 Hz water pressure pulsation in the flow passage is the exciting source of the severe vibration of the factory building under high load.The source of 25 ～ 35 Hz hydraulic pressure pulsation frequency component in the flow passage is calculated and analyzed

which provides a basis for vibration optimization treatment of power house.