Against the backdrop of the increasingly expanding impact of energy transformation, the integration of high proportion of renewable energies and power electronic devices brings challenges to the research of the new power system. The traditional power system is beginning to shift towards a comprehensive dynamic balance of power grid, power source, load and energy storage. The model simulation of the new power system requires more accurate and rapid dynamic simulation to verify. However, there is currently a lack of efficient simulation solutions and effective simulation tools for large-scale electromagnetic transient simulation of the new power system. Based on the domestic real-time simulator (UREP) and taking the Simulink model of the medium voltage distribution network as an example, this paper proposes the concept of "full topology, full electromagnetic transient, and full configuration", and uses ideal transformer model(ITM) segmentation to reduce the order of the system model and multi-core parallel computing technology to kernel the model, the results show that the proposed modeling method not only improves the simulation accuracy of the new power system model, but also greatly shortens the simulation time of the model, which verifies the feasibility of large-scale new power system simulation.