In order to analyze the complex flow field environment inside the mud tank during the dredging operation of the TSHD and improve the safety performance of the ship dredging operation, the hydrodynamic software STAR-CCM+ is used to establish a numerical tank with a TSHD as the research object. The motion response characteristics of the TSHD and the evolution characteristics of the free surface in the tank when the mud door is opened under the action of waves are studied by overlapping grid technology. The results show that the ship resistance and the free surface of the chamber of the TSHD change significantly when the mud door is opened. There is a situation where the free surface sloshing attacks the side wall of the chamber. It is necessary to strengthen the structure of the severely attacked area and adjust the real-time power of the propeller in time. The research results can provide some reference for the structural design of the dredger "s mud cabin.