The invention discloses a low-voltage direct-current power distribution network and a fault isolation method thereof. The low-voltage direct-current power distribution network comprises a power supplylevel line, an intermediate level line and a user level line. The power supply level line comprises a power supply capable of realizing low-voltage ride-through, and a power supply output end is connected with a power supply outlet bus in series. The user level line comprises a direct current load bus which is connected with a third level switch in series to connect an electrical load. The intermediate level line comprises a second level switch which is connected in series between the power supply outlet bus and the direct current load bus. A time difference between a tripping time of the second level switch and a tripping time of the third level switch is at least greater than a tripping time of the third level switch. The tripping time of the second level switch is smaller than a low-voltage ride-through time of the power supply. The tripping current multiple of the second level switch and the tripping current multiple of the third level switch are not smaller than corresponding preset tripping current multiples. According to the method, a fault can be effectively, reliably and rapidly isolated under the condition that a whole network is not powered off.