The invention relates to a multi-circuit DC circuit breaker and a cutoff method thereof. On the basis of a typical hybrid DC circuit breaker topology, the cost of the DC circuit breaker in a multi-circuit net-shaped DC system is reduced by a sharing main branch and an energy consumption branch on the premise of no influence on reliability; a DC circuit is connected to a top point of a polygon, a fault transfer branch is connected in series to each edge in the polygon, the main branch and the energy consumption branch are connected in parallel to interphase edges; when a fault occurs, a switchof the fault transfer branch which is adjacent to a fault circuit and is not connected in parallel with the main branch and the energy consumption branch and switches of all fault transfer branches connected in parallel with the main branch and the energy consumption branch act, a fault current of all feeders at least pass through the main branch and the energy consumption branch to perform cutoffand energy releasing; and when a fault current is reduced to a set threshold, an isolation switch on the fault circuit acts, and the fault circuit is isolated.