Abstract: Frequency invariant beamforming is an important research direction of broadband array signal processing. Considering the application of speech processing based on microphone array, a novel frequency invariant beamforming method based on non-uniform Fourier transformation is proposed to solve the frequency invariant property even for the lower frequencies of FIB in this paper. This proposed method represents Vandermode matrix for non-uniform Fourier inverse transformation, in which the data of low frequency sampling is increased. Then an optimal symmetric window function is presented to process it. The spatial - temporal filter was constructed in the end. Thus not only the approximating expected beam response is obtained even for the low frequency band, but also the number of sensors are reduced. The computer simulation results show that the proposed method is effect