Abstract: The establishing method of Pspice subcircuit was introduced， and self-breakdown switch and high current diode subcircuits were created based on their principles of work， which can describe their working processes. The circuit of Flash Ⅱ accelerator was then built using the subcircuits created as its switches and diode. The simulation results of diode voltage，current and impedance in normal operation and short-circuit state accord with the experimental results. The method of subcircuit establishment and parameters control can be used to simulate the components with nonlinear impedance and complicated working process， and it is favorable for parameters control of circuits with a large number of identical components.