Abstract: The vessel MVDC integrated power system contains a large number of special motors and power electronic devices, which bear the characteristics of high order, large nonlinearity, and great calculation amount of electromagnetic (EM) transient simulation. Using a typical MVDC integrated power system as the study object, this paper first presents an EM transient real-time simulation model for the whole system based on the established models for the multiphase generator rectifier system, the multiphase propulsion motor and its inverter, the isolated DC/DC converter and other special facilities. With the average distribution of switches and the fewest nodes as the goal of optimization, it then proposes a component-based heuristic system partition method to improve the efficiency of calculation for an accurate real-time simulation of the system in the case of using fewer computational resources. Physical tests have been carried out to verify the simulation model, and the comparative analysis proves the proposed portion method to be feasible and effective.