In the environment of shortwave radio communication with all kinds of interferences, it is essential for an accurate and real-time observation of signals. In this article, a scheme for a hardware software co-design of a broadband-intermediate-frequency (IF) multi-frequency shortwave signal observation system is proposed. Firstly, the system samples IF shortwave signals, using the direct IF digital sampling technique performed by the high-speed analog-to-digital converter (ADC), into the field programmable gate array (FPGA) for real-time processing. Secondly, multiple intermediate frequencies are down converted into base band for analysis with FPGA serving as the digital down converter. Finally, multiple display contents including waveform, spectrum and spectrogram are generated by the system. The proposed system provides advantages of miniaturization, portability, real-time and rich display contents.