The invention discloses an MMC sub module circuit with a DC-side fault blocking ability, which relates to the field of power system protection control and has the advantages that short circuit current can be completely locked, the structure is simple, the needed elements are few, and integration is high. The MMC sub module circuit with a DC-side fault blocking ability comprises two half bridge sub modules, a first power switch tube with an antiparallel diode and a diode, wherein one half bridge sub module is connected with the emitter of the first power switch tube with the antiparallel diode, and the other one is connected with the collector of the first power switch tube with the antiparallel diode; the negative electrode of the diode is connected with the collector of a second power switch tube with an antiparallel diode in the half bridge sub module connected with the emitter of the first power switch tube with the antiparallel diode, and the positive electrode is connected with the emitter of a third power switch tube with an antiparallel diode in the other half bridge sub module. the product has a small size, and stability is high; the topological structure is simple, the cost is low, and realization is easy; configuration is flexible power consumption is reduced; and the DC side can be broken in the case of short cirucit, and the response is quick.