Abstract: Aiming at the necessity and functional requirements of the decontamination of the spent fuel storage rack, a underwater flushing decontamination device was developed for the spent fuel storage rack in a second-generation nuclear power plant. The structural composition, functional principle and control system design of the device are introduced in detail. The device is easy to operate and has good flushing and decontamination capability, which greatly reduces the radiation dose level of the spent fuel storage rack.