The invention provides a current interruption characteristic optimization circuit of a current injection type DC circuit breaker. The optimization circuit comprises a vacuum switch, a discharge branchcircuit and an LC resonance branch circuit, wherein the LC resonance branch circuit is connected with the vacuum switch in parallel, the discharge branch circuit is connected with a capacitor of theLC resonance branch circuit in parallel, and the capacitor of the LC resonance branch circuit realizes the discharge voltage reduction during the low current interruption process of the DC circuit breaker through the discharge branch circuit. The optimization circuit not only improves the low current interruption characteristic under the premise of maintaining the high fault current interruption characteristic, but also avoids the increased equipment complexity, high loss and low reliability caused by a series saturable reactor in the prior art at the same time. Meanwhile, the invention can further omit a buffer branch circuit structure of the novel current injection type DC circuit breaker at present, and greatly increases the equipment reliability.