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Due to numerous advantages of thyristors, such as low conduction loss and low cost, using thyristors to design solid-state circuit breakers (SSCBs) to protect dc microgrids has become increasingly popular. However, the majority of existing bidirectional thyristor-based SSCBs (TCBs) have one or more following drawbacks: high conduction loss, lack of operating current interrupting ability, low current breaking reliability, unsuitable for fast-reclosing protection, and the need to use ample thyristors. To address these problems, a new bidirectional TCB is proposed in this article. First, the proposed method could break both bidirectional operating and fault currents reliably by actively turning on its auxiliary thyristors. Second, the conduction loss of the proposed TCB is extremely low. Third, the proposed TCB can realize fast-reclosing protection function by masterly using an LC resonant circuit, which would ensure a safe restart of dc microgrids after a fault. Finally, the proposed TCB is very economical since only one additional set of auxiliary parallel thyristors is needed. Thus, all the above merits are making the proposed TCB a promising candidate for protecting dc microgrids. The parameter design guidelines, scaled-down experimental results, and comparative studies of the proposed TCB are also presented.