Abstract: In nuclear reactor, subjected to the axial flowing coolant, the fuel rod may vibrate. This vibration can cause cladding deformation and fretting wear that have an important effect on safety and economy of the entire nuclear power plant. Study on the vibration characteristics of the fuel rods with spacer grid is necessary for studying the fretting wear. In this paper, based on the Euler-Bernoulli beam theory, dynamic mesh technique was used to deal with the fluid-structure interaction numerical simulation by Fluent. The influence of the main fluid parameters on the RMS (root mean square) of vibration displacement, such as turbulence intensity and axial velocity, and the mechanism of flow-induced vibration in axial flow were analyzed in detail. The numerical results show that the RMS of the vibration displacement of the fuel rod increases with the flow velocity, and the pressure pulsation on both sides of the fuel rod is one of the factors causing the vibration. The existence of the spacer grid changes the position of the large vibration displacement and significantly enhances the vibration response.