Abstract: A Fast Fourier Transform (FFT)method for the data processing of dynamic mechanical property in the frequency domain is presented. Its efficacy compared with the timedomain method used in the commercially available instrument was verified in the selfmade dynamic viscoelastometer. The FFT method shows its merits. It has better reproducibility and noise-suppression performance than the time-domain method. It can be used for determining the dynamic mechanical frequency spectrum and nonlinear viscoelasticity of high polymers.