Abstract: Research on flow-induced vibration (FIV) of the parallel-plate fuel assembly plays an important role in the reactor safety analysis. In this paper, the vibration mechanism of a simplified double-ends-fixed flexible plate in the rectangular channel was researched, which lays the foundation for the flow-induced vibration research on the parallel-plate fuel assembly. In the experiment, the natural frequency and actual elastic modulus of the plate were investigated with an acceleration sensor, and the relative vibrant frequency and displacement were measured by strain gauges and laser displacement sensor in different velocities. The results indicate that the plate vibration in the water behaves as a complicated turbulence-induced one. The higher the velocity is, the bigger the vibration displacement is. With the velocity increasing, the plate vibrates-severely. The low frequency reduces, while the high frequency increases.