The invention relates to a device for preventing hydropower station pressure steel pipe resonance. The device comprises a pressure transmitter, an electric ball valve, a control system and an alarm device, the pressure transmitter is installed below an upstream pressure steel pipe and is connected with the control system through a cable, the control system is connected with the electric ball valveand the alarm device through cables, and the electric ball valve is connected to a drainage pipe below a ball valve. In the prior art, a method for preventing pressure steel pipe resonance is normally to replace a packing according to the packing abrasion condition, normal starting and stopping of a unit can be influenced, and the economical benefits are reduced; and according to the device, thecontrol system is used for releasing high water pressure generated by self-oscillation according to pressure monitoring values, and the resonance generation condition is damaged to achieve the aim ofavoiding the pressure steel pipe resonance. Device running cannot influence normal starting and stopping of the unit, the unit halt overhauling time number is decreased, and electric quantity losses caused by overhauling and damage caused by the resonance are avoided.