The invention relates to a quick low-voltage power supply fault isolating device with an automatic load balance function. The quick low-voltage power supply fault isolating device comprises an incoming line measuring unit, an outgoing line measuring unit, a signal acquiring and processing unit and a relay protection and switch control unit. Under the condition of no faults, the signal acquiring and processing unit controls various outgoing line switches to realize the automatic load balance function through the relay protection and switch control unit; under the faulty condition of a bus, the signal acquiring and processing unit controls various incoming line switches and outgoing line switches to realize quick fault isolating function through the relay protection and switch control unit. The quick low-voltage power supply fault isolating device can realize the automatic load balance function, line loss is reduced, and benefits are increased. Meanwhile, quick isolation of faulty lines is realized, and reliability and stability in power supply for important users are effectively improved.