This paper proposes a real-time simulator for DC microgrids research. The simulator is implemented with different computation modules which simulate designated generation, storage, and load of the microgrid. The backbone of the microgrid is simulated as well using one computation module. To verify the proposition, a boost converter, DC load with periodic consumption, and the transmission line structure is firstly simulated with real circuit elements as well as C-code modules. The distributed real-time simulation hardware platform is built using LAN router as the data exchange equipment, and the experimental results further verify the accuracy and feasibility of the distributed circuit model of DC microgrid. In the real-time digital environment, the fault control and propagation mechanism of DC microgrid are analyzed in detail, laying the foundation for future research.