Abstract: The study of fluid-structure interaction (FSI) problems in elastic structures is crucial for accurately predicting the coupling between water flow and structural behavior in hydraulic engineering. A numerical model of an elastic plate impacted by dam failure-induced water flow is established using the smooth particle hydrodynamics (SPH) method. The validity and advantages of the SPH model are verified through physical model tests and comparisons with the finite element method (FEM) from multiple perspectives. Building on this foundation, the characteristics of fluid-structure interaction under the impact of free surface flow are further analyzed by examining the flow field properties, flow-structure forces, and the structural spectral variation patterns. The results indicate the following: ①A velocity jump between the water flow and the sharp curvature of the free liquid surface leads to vortex formation at the cavity. ②The water flow over the elastic plate generates clockwise vorticity, while the water flow that hits the wall and re-contacts the elastic plate creates counterclockwise vorticity due to the difference in flow velocity. ③The force exerted by the water flow on the structure shows a pattern of increasing, then decreasing, and increasing again, with smaller deformation of the elastic structure corresponding to greater force. ④The vibration frequency along the elastic structure decreases gradually from the fixed end to the free end. Larger deformation of the free end weakens the vibration response, with the first-order frequency decreasing from 2.88 Hz to 2.44 Hz, the second-order frequency from 6.24 Hz to 5.68 Hz, and the third-order frequency from 9.57 Hz to 8.96 Hz. These findings provide valuable insights and guidance for addressing fluid-structure coupling problems.