The time series of instantaneous velocity in the Kenics static mixer, 0.04 m in diameter and 1.25 in aspect ratio, were conducted with laser Doppler particle analyzer. The signal of velocity fluctuation were decomposed into signals of different frequency band including 0~12.5, 12.5~25.0, 25.0~37.5, 37.5~50.0, 50.0~62.5, 62.5~75 Hz and more than 75 Hz based on Fourier transform. The linear and nonlinear correlation characteristics of signal of different frequency band were evaluated with auto-correlation function and mutual information function, respectively. The experimental results indicate that the signals of more than 62.5 Hz in frequency have no linear correlation, and there are no nonlinear and linear correlation for the time series signal which is over 75 Hz in frequency.