High-power solid-state devices are introduced to electromagnetic launchers (EML) as leading switch technology, which make the systems superior of improved energy efficiency and reduced volume. The semiconductor device models available in most circuit simulation software packages do not accurately characterize high-power thyristors for thermal management and snubber design. A simple PSpice model for high-power thyristor is proposed, which is based on the device behavior rather than on the physical structure. The model is used to analyze capacitor-based pulsed power circuits for experimental railgun system. Extensive simulations have been performed to examine the model characteristics. Also, the factors influencing waveform of discharging current and system efficiency are discussed.