Abstract: Based on the analysis of the ex-core neutron noise signal in multiple fuel cycles in Fangjiashan and Ningde Nuclear Power Plants, the beam mode vibration frequency and amplitude characteristics of the core barrel is obtained. These characteristics are applied to other nuclear power plants, and the problem of larger amplitude with barrel beam mode in a nuclear power station is found. The trend of beam mode vibration frequency and amplitude, the drift of frequency, and the growth rate of amplitude are analyzed and diagnosed. No obvious support deterioration in the barrel is found, and the condition under which the plant can continue to operate is given.