Fast Fourier transform (FFT) plays a key role in digital signal processing. With the increasing demand of high performance ultra-long point FFT, digital signal processor (DSP) is becoming more and more difficult to meet the demand, so integrated FFT accelerators have become an important development trend. In order to support ultra-long point FFT, this paper extends the two-dimensional decomposition algorithm of FFT to multi-dimensional, and we propose a high performance ultra-long point FFT accelerator architecture which can be integrated into DSP. In this architecture, three-dimensional transposition operation is realized by using collision-free addressing method with prime number memory banks; efficient twiddle factor generation is realized by recursive algorithm; FFT operation circuit is refined by using single precision floating-point fused dot product and fused add-subtract operation. Finally, this paper realizes the single precision floating-point FFT calculation within 4G points. The synthesis result shows that the proposed FFT accelerator can run at a frequency of more than 1GHz and its performance can reach 640Gflop/s, which has been greatly improved in terms of points and performance compared with the existing research.