Abstract: Based on the analysis of two-dimensional Fourier transform method (2-D FFT), a mixed-spectral estimation was proposed combined with FFT and AR model for the recognition of Lamb wave propagating model in aluminum plates. Experimental results showed that the mixed-spectral estimation could detect the ultrasonic phase velocity of multi-mode Lamb wave accurately, compared with the conventional two-dimensional Fourier transform methods, the resolving power of the new method was highly increased. The mixed-spectral estimation methods could be widely used for development of ultrasonic guided wave testing.