In previous times, the full bridge converter flow model is built on more loss and neglected parasitic circuit parameters based on the low voltage high current output under the circumstances, these parasitic parameters can not be neglected. This paper, considering the loss of some parasitic parameters such circumstances, establishes the new system model. It combines with full-bridge converter times the flow of small signal analysis to do design correction. Simulation results indicate that this modeling method compared with not consider all the parameters of parasitic modeling method is better with the actual circuit performance.