The invention discloses an underwater reef crushing test device. The underwater reef crushing test device is characterized by comprising a water sump, wherein the water sump is provided with a three-dimensional motion control system, and also provided with a spraying nozzle and a splitting mechanism which are installed on the three-dimensional motion control system. The underwater reef crushing test device disclosed by the application can carry out simulation tests for underwater reef cutting, and can simulate construction conditions to carry out cutting tests, thereby improving the safety, success rate and efficiency of actual cutting construction.