Abstract: As a new soft computing, rough set (RS) has huge potential in data mining. RS can analyze and handle imprecise, inconsistent and incomplete data efficiently. The pulsed power device has many faults due to complicated components. An overall simulation of a typical pulsed power device based on PSpice software was built. In this model, several typical faults were simulated, and the parameters of the fault waveforms were analyzed by RS. Some diagnostic rules that have wider applicability were deduced. This work lays the foundation for further study.