A central computer system framework of software radar is designed based on GNU Radio, which is an open-sourceradio platform. This make it more quickly in radar design and development, and let the components of central computer can bereconfigured. Central computer processing time is reduced significantly by multi-thread. Simulation accuracy is ensured byoptimizing and controlling program running sequence. And components of radar communicate by message mechanism. Afterhardware-in-the-loop simulation testing, it is found that the framework can simulate radar’s searching and tracking targets inreal-time, meanwhile, the component can be reused and reconfigured.?