Abstract: Through analyzing the characteristics of symmetric multi-processor (SMP) parallel processing system, a very large fast fourier transform (FFT) algorithm is proposed. This algorithm significantly reduces the dependence on memory and improves FFT's performance by taking the limited rules of one-dimensional sequence split, changing the twiddle factor calculation method, and optimizing the data distribution and storage access. Experiment results show that the algorithm is suitable for SMP platform and can effectively solve the problem of very large FFT, which single-core processor harder to realize.