Abstract: The flow-induced vibration phenomenon of steam generator U-tube may threaten the operation safety of nuclear power system, which must be considered in the design and operation of steam generator. In this paper, the CFD software FLUENT is used to establish the equivalent two-dimensional calculation model of the flow around the heat transfer tube. The structural dynamics equation is solved by the user-defined function（UDF）, and then combined with the dynamic grid model, the fluid structure coupling numerical simulation of the flow-induced vibration phenomenon of the steam generator U-tube is realized. The lift coefficient, drag coefficient and vortex shedding frequency of the fluid under the condition of fixed tube and vortex-induced vibration are calculated, and the vortex-induced vibration displacement of the tube is obtained. Finally, the influence of Reynolds number and tube restraint mode on tube vibration is revealed. The work in this paper can provide reference for safety analysis and optimization design of steam generator.