Abstract: In order to analyze the dynamic response of the reactor structure, a three-dimensional nonlinear was established. The model overcame many nonlinear factors such as clearance, contact, friction, damping, pretension, impact, fluid-structure coupling and connection stiffness. Considering the fluid-structure coupling between the core barrel and the RPV, the hydrodynamic mass matrix was modeled and verified by ANSYS acoustic element. Three-dimensional upper core plate, lower core support plate was set up. Multi-group fuel assembly was built, which considered the preload and bounce with the core plate, the clearance and impact with the core shroud. The model accurately simulated the dynamic response of the reactor structure because of the coupling of horizontal and vertical directions. Finally, the response of each component was obtained by inputting the time history of the impact acceleration in three directions, which provided the input for the stress analysis of the components and the impact experiment of the control rod drive line. The method in this paper can offer a reference for the three-dimensional nonlinear dynamic analysis of the reactor structure.