This paper studies the realization method of QPSK modulation and demodulation circuit based on FPGA.And the simulation results are given under the environment of MAX+PLUSII .In this paper, the scheme uses phase selection method, compared with the modulation and demodulation method commonly used, design more simple, more suitable for FPGA implementation, the reliability of the system is higher.Through the analysis of the simulation waveform shows, the very good realization of the QPSK modulation and demodulation function.