Underwater switching device realizing light and heavy assembly load simulation integration of refueling machine of nuclear power plant

The invention applies to debugging and regular tests of a refueling machine of a nuclear power plant, particularly relates to an underwater switching machine realizing light and heavy assembly load simulation integration of the refueling machine of the nuclear power plant and aims to solve the problem that the light and heavy assembly load modes cannot be switched by a conventional device underwater. The underwater switching device is characterized by comprising a bottom plate, a supporting frame, a basic weight module, an underload counterweight compensation module, an overload counterweight compensation module, a lifting rod, a grabbing module, a top plate, lifting lugs, an overload counterweight compensation module support ring, an underload counterweight compensation module support ring, a basic weight module support ring, a heavy assembly compensation module and a lifting plate. With the adoption of the underwater switching device, load difference values under two modes including a light fuel assembly and a heavy fuel assembly can be compensated, switching can be finished underwater, integrated design of load, overload and underload test devices for the refueling machine is realized, and device structure change or accessory increase or decrease is not needed in a test process; besides, the underwater switching device adopts stainless steel machining and has low probability of being corroded by a boric acid solution.