Abstract: With the rapid emergence and profound penetration of modular multilevel converters (MMC) in power system, the real-time simulation technology of electromagnetic transient (EMT) becomes very important. In order to realize the real-time simulation of the MMC-based flexible HVDC system, a real-time System-on-Chip (SoC) simulation model is proposed for MMC, which is applicable to field programmable gate arrays(FPGA). Based on this EMT model, the MMC arm is made equivalent to one Thevenin’s circuit, which keeps the number of nodes unchangeable when MMC level varies, thus greatly accelerating the simulation process. This method can not only suppress the numerical oscillation under faults, but also realize the real-time simulation of multiple sub-modules. The PSCAD simulation results have verified the accuracy and efficiency of the proposed model and corresponding calculation method, and the dynamics of both sub-module level and system level can be reflected accurately and efficiently.