This paper presents a hardware software co-design of embedded digital spectrum analyzer. As a digital hardware design, it achieves better portability and modularity so that it could be easily deployed and embedded into other systems as a module and conduct arbitrary intermediate nodes spectrum monitoring with ease while such tasks are hard for traditional spectrum analysis instruments to accomplish since most of them only provide limited user interface. Besides, this design implements functions of real-time signal analysis and real-time spectrum display with VGA port, which traditional embedded data observation systems, for example SignalTap II Logic Analyzer, do not have. Furthermore, this design serves as a sample of hardware software co-design of soft-core processor based system, which can be used for reference.