Abstract: Assuming that all supports were valid, based on the results of fuel rod modal analysis, according to the flow field distribution characteristics of PWR fuel rods, the power spectral density was used to characterize the turbulence excitation. Combining the correlation power spectral density test parameters, the mean square value of the vibration displacement of each mode was found, and the wear depth of dimple position of the fuel rod was calculated based on the ARCHARD wear formula. Due to the manufacturing process, transportation and irradiation, the clamping action of the grid to the fuel rods may relax. Assuming that just one single dimple or spring relaxation is in turn, the effect of grid relaxation on the fuel rod modes, flow-induced vibration and wear were studied. The results show that the relaxation of the grid spring has negligible effect on the natural frequency. The dimple relaxation near the location with larger original amplitude has a significant effect on the natural frequency. The transverse flow velocities at the inlet and outlet of the core are larger and the amplitudes of turbulent excitation at the bottom and top of the fuel rods are larger when all supports are valid. When dimple relaxes in these locations the amplitude of turbulence excitation will obviously increase. The effect of dimple support relaxation in the middle position on amplitude is less. The effect trend of dimple support relaxation on the depth of wear is basically the same as the effect on the maximum amplitude of turbulence excitation. In addition to the amplitude of turbulence excitation, the wear is also related to the natural frequency. The effect of multiplying the top mode and frequency is greater than that of the bottom grid, so the top grid dimple relaxation has the greatest effect on the wear.