A bidirectional modular multilevel DC-DC converter (Bi-MMDC) with inherent voltage balance capability for high/medium voltage applications is proposed in this paper. The proposed converter adopts modular half-bridge-type structure for both of the primary and secondary sides, which can reduce the voltage stress of the switch devices. The foundation of this derived topology stems from combination of the modular multilevel DC-DC converter and the dual active bridge structure. Furthermore, the voltage balance of submodule is achieved automatically through circulant modulation, which ensures the safe operation of the proposed converter. What’s more, bidirectional power flow is enabled based on the phase-shift control. The simulation is built and tested to verify feasibility and effectiveness of the proposed topology and modulation schemes. The simulation results have demonstrated that the voltages of all submodule capacitors are intrinsically balanced, naturally maintaining equilibrium without external intervention, ensuring stable operation and optimal system performance, and the energy is capable of flowing in both directions.