The invention relates to a high-voltage DC circuit breaker and an energy supply device thereof. The energy supply device comprises n cascaded energy supply transformers, wherein the energy supply transformer of each stage comprises a set of iron core, two sets of primary windings which are mutually redundant and two sets of secondary windings which are mutually redundant; the two sets of primary windings of the first stage energy supply transformer are used for coupling with two energy supply power sources which are mutually redundant respectively; and the two sets of secondary windings of theenergy supply transformer of each stage are each provided with an output terminal for supplying energy to corresponding valve layers in a valve tower of the DC circuit breaker. Through serially connecting multi-stage transformer in series, the transformer of each stage adopts one set of transformer iron core, two sets of primary windings and two sets of secondary windings, the two sets of primarywindings serve as two sets of power sources used for redundant power supply to the corresponding layer power module of the DC circuit breaker, the redundant standby of the energy supply device can berealized without increasing the size and floor space of the energy supply transformers, and the operational reliability of the high-voltage DC circuit breaker can be improved.