The quadruple-level circuit model for stack and vacuum section of Julong-I facility was established. To avoid complicated two-dimensional circuit simulation, the prediction-correction method was used to deal with the distribution of currents at the entrance of the quadruple-level insulation stack. The accuracy and efficiency were both ensured by this method. By applying this model to the FCM-PTS code coupled with the snow-plow model for the Z-pinch load, the current for each level of the outer magnetic insulation transmission line was obtained, while the coincidence of load currents between simulation and experiment was also improved.