Abstract: Toward the characterization of early stage damage of structures by nonlinear ultrasonic testing technology, a dynamic wavelet fingerprint (DWFP) analysis method was developed for nonlinear ultrasonic signal analyzing, and nonlinear characterization parameter of early damage based on DWFP distribution was proposed as well. Meanwhile the influence of different wavelet basis functions and scale extents on nonlinear ultrasonic effects extraction is investigated, and the optimal wavelet basis functions and scale extents sensitive to early stage damage are obtained. After that, DWFT analysis method was applied to harmonic and frequency-mixing nonlinear ultrasonic test signals analysis. It has been shown that DWFT analysis method can effectively extract the harmonic and frequency-mixing components embedded in testing signals, and nonlinear characterization parameter based on DWFP distribution is capable of quantifying characterization of micro-crack in plate structures. Useful exploration is done for nonlinear ultrasonic testing signal analysis.