Abstract: With the continuous development of DC power system, DC fault protection problems are becoming more prominent, circuit breakers are widely used to isolate faults. Thyristor-based solid state circuit breakers demonstrate low losses and low costs, but the characteristic that thyristors can not be controlled to turn-off has limited the development of these circuit breakers, some current solutions have disadvantages of unreliable reclosing and high losses. This article proposes a novel bidirectional DC solid state circuit breaker; reliable active turn-off, soft reclosing and MOV off-state leakage current elimination create advantages in high reliability and low losses. The working principles in three modes and parameters design are described in detail. Simulations and experiments show that the proposed topology can actively interrupt short-circuit faults, and distinguish the type of fault by soft reclosing.