Abstract: Stepped frequency chirp signal is an important signal form to improve range resolution in radar system. It effectively reduces the requirements of high-resolution radar target on hardware system bandwidth, and reduces the requirements of bandwidth in DDS signal generator and AD sampling rate in data acquisition unit in the form of multiple narrow-band signal synthesis. Hardware-in-the-loop simulation can verify the radar signal performance conveniently, efficiently and cheaply. The main instruments used in building the hardware-in-the-loop simulation system are signal generator and spectrum analyzer. In the simulation, wideband synthesis is performed in the frequency domain, and then the IFFT is carried out, which is transformed into the time domain, and the resolution of the distance of the signal is judged by comparing the main lobe width of the signal. The experimental results show that the range resolution increases with the number of steps. Through the hardware-in-the-loop simulation, the technical route of using stepped frequency modulation technology to improve range resolution is verified, and the preliminary technical scheme and parameter optimization method are provided for the actual radar system design.