Abstract: Measurements on vortex-induced elastic thin plate with a 3D-particle image velocimetry (3D-PIV) system and a motion tracking system (DH-5935N) are carried out for understanding the mechanism of the fluid-structure interaction.The flow field near the plate is measured with the 3D-PIV system while the motion of the elastic thin plate is measured with the motion tracking system of the accelerating sensor.In the experiments,macroscopic interprets on the fluid-structure interactions are made using three-dimensional vector fields of the flow and displacements of the elastic plate.Resultsof motion measures show that the fluid-induced vibration is quite significant for flow Reynolds numbers and the elastic plate shows complex non-periodic and non-symmetry coupled vibrating behavior when the complex wake interacts with the plate,simultaneously,and PIV result shows the interchange of flow patterns with the fluid-induced vibrating plate.