The power spectral density [15] (PSD) of the signal is the statistical result of the response of the structure under the excitation of random dynamic load. It is the relation curve between power spectral density and frequency. The power spectral density can take the form of displacement power spectral density, velocity power spectral density, acceleration power spectral density and force power spectral density. Mathematically, the area under the curve of the relationship between power spectral density and frequency is the mean square value. When the mean value is zero, the mean square value is equal to the variance, that is, the mean square value of the response standard deviation.