One embedded diagnostics system for radar is designed based on the requirements of fault detection, diagnosis and maintenance. The paper introduces the theory of design, diagnosis strategy and method of realization from system frame and software architecture two aspects. The system realized BIT monitor, automatic testing and integrated fault detection via an embedded structure design and philosophy of software refer to constructional element. The system is provided with generality, portability and expansibility. The application has proved the system stable performance, easy operation and maintenance, has a higher application value.