Herein, we implement a software-in-loop simulation (SILS) system for fighter radar systems. The implemented SILS system simulates fighter radar environments and hardware by mathematical modeling, generates radar-simulated digital signals, and stores/analyzes simulation results. It includes a personal computer (PC)-based virtual radar processing unit, which can be used to develop radar control and process algorithms and codes and can also examine the functions and performance of the software and code of actual radar processing equipment by connecting actual equipment. Because antenna and transceiver models are included, the performance of the initial hardware designs at the system level can be examined in the simulation environment, thereby increasing the hardware design and development speed. We demonstrate the validity and usefulness of the SILS system, implemented using the radar environment and hardware mathematical models obtained from the development of fighter radars for numerous years, through SILS-based test results.