Unlike ac systems, there is no zero crossing to extinguish the arc that occurs on breaker opening. With the rapid development of EHVDC, VSC-HVDC and DC distribution calling for the use of DC circuit breaker, more and more work has been done in recent years on this aspect. The paper firstly summarizes the sort, configuration and characteristics of mechanical DC Circuit Breaker, Static DC Circuit Breaker and Hybrid Mechanical-Static DC Circuit Breaker at the present and introduces the dynamic research and application at home and abroad. The key issues in the simulation and research of DC Circuit Breaker are establishing the mathematic model of the electric arc, the techniques about equal sharing of voltage and current series and parallel connection of Static electronic devices and Auxiliary circuits in DC Circuit Breaker. This paper summarizes and highlights these three key issues. And finally it includes difficulties of the research about DC circuit breaker in recent years.