Abstract: The switching junction capacitance plays a predominant role during the realization of the switching transient process in high switching frequency resonant DC-DC converters. However, incorporating the junction capacitance into the binary resistor model significantly increases simulation time step and calculated amount. Therefore, this paper proposes a real-time simulation method that takes the switching junction capacitance into account. Firstly, by establishing equivalent state equation, the converter model is divided into system-level model and device-level model to reduce the multiplicative computation of model matrix. Secondly, a dual-clock domain field-programmable gate array (FPGA) implementation scheme is adopted to optimize the timing path. Finally, the real-time simulation model of the full-bridge LLC resonant converter with 250 kHz switching frequency is realized on FPGA. The simulation time step of the system-level model is 50 ns, and the simulation time step of the device-level model is as low as 10 ns, which verifies the practicability of the proposed method in the fast simulation of switching transient. From the results of FPGA resource consumption and experimental comparison, the modeling method proposed in this paper can achieve low FPGA resource consumption and high precision.