Abstract: the Due to the limitation of the optical-mechanical platform of the laser heterodyne interferometry system, the Doppler frequency shift cannot be simulated. Moreover, commercial signal generators cannot realize various types of high-complexity intersatellite heterodyne interference signal simulations. It is difficult to conduct ground tests of the phasemeter for space gravitational wave detection detailed. Therefore, the characteristics of heterodyne interference signals were analysed, the realization principle and method of the signal simulation system were studied, and then the simulation system of the laser heterodyne interference signal for space gravitational wave detection was designed. First, the simulation of the heterodyne interference signal was applied to the DDS. Then, the influence of the Doppler effect was simulated by offsetting the overall frequency. Next, based on the mixed congruential algorithm, shot noise was generated and modulated into the heterodyne interference signal. Finally, with the usage of FPGA, the system hardware platform was built. The time domain and frequency domain characteristics of the generated signals were analysed by an oscilloscope and a spectrum analyser. The experimental result shows that the spurious suppression of the system is −53 dBc and the harmonic suppression is −47 dBc at 2-20 MHz. The signal generated by the system is in good agreement with the expec-tations which satisfies the ground test requirements of the phasemeter for space gravitational wave detection.