In this paper, an efficient solution of MIMO FFT/IFFT processor for IEEE 802.16 WMAN is presented. By applying the proposed mixed-radix dataflow scheduling (MRDS) technique, the effective hardware utilization can be raised to 100%. Therefore, a single butterfly unit within each pipeline stage is sufficient to deal with the two data sequences, and the hardware complexity is significantly reduced. The proposed FFT/IFFT processor has been emulated on the FPGA board. The signalto-quantization noise ratio (SQNR) is over 44 dB for QPSK and 16/64-QAM signals. Furthermore, a test chip has been designed using standard 0.18-μm CMOS technology with a core area of 887×842 μm2. According to the post-layout simulation results, the design consumes 46 mW at 64 MHz operating frequency, which meets the maximum throughput requirements of IEEE 802.16 WMAN.