Concerning the problems of the blind source separation algorithm that is not suitable for the broadband, complex computation, and being acute to various Signal Noise Ratio (SNR), a beamspace Blind Source Separation (BSS) method based on sub-band decomposition was proposed. The method of sub-band decomposition was used to realize the expansion of blind source separation under broadband condition, and beam transforming was used to reduce the amount of calculation. Simulation results demonstrate that the proposed method exhibits good source signal estimation capability. Even without any prior knowledge, it has the same performance as Root-Music high resolution algorithm.