Abstract: Based on the fluctuating pressure data obtained in the flow- induced vibration test of reactor pressure vessel internals scale model, the distribution characteristics of fluctuating pressure power spectral density are analyzed at different positions on the core barrel surface, and the correlation length characteristics of fluctuating pressure power spectral density are obtained based on the correlation analysis. The power spectrum density of the fluctuating pressure on the core barrel surface is broadband attenuation spectrum with a very rich frequency andecreases quickly with the increasing of the frequency and then tends to be gentle; The fluctuating pressure power spectral density is basically the same in the region located at the same height on the core barrel, but the differences of the PSD (power spectral density) are obvious between the regions at different heights. The correlation length of the fluctuating pressure power spectrum density decreases sharply with the increasing frequency and then tends to be constant. The flow-induced vibration response of the core barrel has little effect on the fluctuating pressure power spectral density and it is reasonable to simplify the flow-induced vibration of the core barrel into the weak coupling problem.