A new topology of DC hybrid circuit breaker based on two-stage commutation has been proposed in this paper. In normal current breaking, the current is commutated by utilizing the arc voltage across high-speed switch (HSS). In fault current breaking, the current is cummutated in two stages, which not only achieves the arcless open of HSS, but also lowers the over-voltage rate of rise. The influence of the arc voltage on the commutation time and arc energy in normal current breaking is investigated experimentally. Then, the simulation model of the fault current breaking under different current rates of rise in medium voltage DC (MVDC) system is established on MATLABSIMULINK platform. Finally, the breaking over-voltages for the single-stage and two-stage commutation topologies in fault current breaking are compared. The simulation results show that the topology with two-stage commutation can improve the breaking reliability greatly.