In order to test and repair a kind of Microwave Landing Equipment, a design method of Microwave Landing signal simulator is proposed. Firstly, the basic principle and signal format of microwave landing system are briefly introduced, and the concrete realization method of DPSK modulation is discussed. And then use FPGA to synthesize the Microwave Landing baseband digital signal which is set according to the parameter of the host computer. After conversion by DAC, it is input to the IQ modulation module to up converting to RF signal. Finally, the RF signal is output after filtered and the gain. In order to facilitate the control of analog signals, the PC software developed on the Lab Windows/CVI platform has the flexibility to set the analog signal type, frequency channel, analog azimuth and output power. The output signal is tested with oscilloscope and spectrum analyzer. The test results show that the parameters can meet the design requirements. And the design method reduces the analog link, streamlining the hardware structure, and control more flexible.