Abstract: The hybrid DC circuit breaker is the key equipment to realize the fast interruption of fault currents and ensure the continuous and reliable operation of VSC-based DC grids to the greatest extent. At present, the hybrid DC circuit breaker based on the cascaded full-controllable power electronic modules suffers from problems of high cost, complex control and difficult to large-scale applications. To solve this problem, a novel hybrid DC circuit breaker based on current injection is proposed in this paper. The capacitor of the oscillation branch is pre-charged by the DC system, and thyristors are used to control the resonance between the capacitor and inductor in the oscillation branch for the purpose of assisting the rapid commutation of fault currents, and as a result the fast interruption of fault currents is achieved. The basic principle of LC resonant circuit was analyzed firstly. Then, operation principles of the proposed hybrid DC circuit breaker was elaborated in detail. Finally, the effectiveness and applicability of the proposed hybrid DC circuit breaker were verified with PSCAD/EMTDC software.