In practical engineering, the radial gate and gate pier are closely connected and interact with each other under the fluctuating pressure of water flow, forming an integral gate-pier system. In order to understand the interaction between the gate and the pier, the fluid-structure coupling theory is adopted to study the flow induced vibration of the radial gate-pier system. Taking the radial gate of a certain water conservancy project as an example, three-dimensional finite element models were established for the single body of the radial gate and the radial gate-pier system to calculate their natural vabration frequencies. Then the dynamic responses of the two models were analyzed based on the results of modal analysis, by which the mutual influence laws of the gate and pier in terms of dynamic characteristics and flow induced vibration response were summerized. The results show that the pier has a significant influence on the dynamic characteristics and response of the gate. When considering the influence of the pier, the natural vibration frequency of the radial gate decreased, with the fourth order natural vibration frequency decreasing the most by 61.45%, which mainly manifested as the support arm vibration. Furthermore, the horizontal displacement of the panel along the river decreased by 44.58% and that of the support arm increased by 37.93%; consequently, the dynamic stress of the panel decreased by 41.70% and that of the support arm increased by 30.71%. Likewise, the flow induced vibration of the gate has a significant impact on the stress of the pier, which increased by 4.713 MPa compared to the maximum stress calculated by the dynamic coefficient of the pier. The radial gate-pier system model can more accurately and comprehensively evaluate the safety characteristics of the radial gate and pier under flow induced vibration compared to conventional methods.