With the development of computer simulation technology, the digital twin of equipment can be realized by combining the actual radar workflow and processing algorithm, so it can be separated from the traditional RF equipment or semi-physical hardware platform. This paper introduces the signal-level simulation of active radar search, tracking and SAR imaging, the functional-level simulation process and related implementation algorithms of passive radar search and tracking, and integrates the algorithms through the active and passive radar simulation basic operation software. Under the closed-loop simulation verification platform, it interacts with the control, scattering source and radiation source subsystems, realizes radar processing in each mode according to the control instructions and echo data input, and finally feeds back to the control subsystem to realize the closed-loop simulation. The experimental results verify the correctness of the workflow of the simulation technology and the correctness of the signal processing algorithm. The analysis of some interference processes further shows that the technology has a wide range of application prospect in the pre-research and review of airborne active and passive radar equipment.