The multiterminal DC distribution network not only has a large number of nodes, but also contains more power electronic devices. Limited by the processing capacity of a single simulator, it is difficult to realize the realtime simulation of the multiterminal DC distribution network. In order to realize realtime simulation of multiterminal DC distribution network, the ideal transformer model method is utilized to model the multiterminal DC distribution network. The DC grid is considered as the boundary, and the converter stations and their AC systems are treated as a subsystem. The subsystems exchange data through ideal transformer model. Finally, a 5terminal DC distribution network is taken as an example and the system is divided into five subsystems. The dynamic responses in different cases of segmented method are compared with the original integral model then. The dynamic responses of the two kinds of models are nearly the same. The feasibility and effectiveness of the proposed model segmentation method is verified.