The invention relates to the technical field of electric flood prevention devices, in particular to a flood prevention device for a transformer substation. The flood prevention device comprises a bottom plate, a supporting plate and a guide rod, and side plates are fixed to the left side and the right side of the top of the bottom plate. The flood prevention device is reasonable and compact in structure and convenient to use, a power transformation box is prevented from being flooded during rainstorm or flood, potential safety hazards are reduced, and normal work of the power transformation box is guaranteed; components such as a compression spring, a fixing block and a hydraulic telescopic rod are combined, so that the stability of fixing the power transformation box on the supporting plate is improved; in addition, the expansion degree of the compression spring is adjusted, so that the device can be used for flood prevention of power transformation boxes of different sizes.