Abstract: Fast Fourier transform (FFT) is a most time-consuming algorithm in the domain of digital signal processing (DSP). The performance and energy efficiency of FFT will make significant effect on different DSP applications. Thus, this paper presents a high energy efficiency variable-size FFT accelerator based on matrix transposition on DSP chip. Several parallel schemes are employed to exploit instruction level parallel and task level parallel of batch of small-size FFTs or big-size Cooley-Tukey FFT. A “Ping-Pong” structure of multi-bank data memory (MBDM) is presented to overlap the overhead of data move and FFT calculation. Moreover, based on MBDM, fast matrix transposition algorithm with basic block transposition is presented to avoid the matrix access with column-wise and improve the utilization of DDR bandwidth. Hybrid twiddle factor generating scheme, combining lookup table and on-line calculation with CORDIC, is presented to reduce the hardware for twiddle factor. Experimental results show that our FFT accelerator prototype with power efficiency of 146 GFLOPs/W, achieves energy efficiency improvement by about two orders of magnitude with multi-thread FFTW on Intel Xeon CPU.