The invention discloses an uninterruptible power system and an operation method of the uninterruptible power system. The uninterruptible power system comprises an electric power distribution device and an electric power redundancy device. The electric power distribution device comprises a plurality of power supply units, and the power supply units receive an external alternating current power supply and convert the external alternating current power supply into a first direct current output power supply to supply power for a direct current load. The electric power redundancy device comprises a plurality of electric power conversion modules, and the electric power conversion modules receive an external direct current power supply and convert the external direct current power supply into a second direct current output power supply to supply power for the direct current load. When the external alternating current power supply supplies power, the direct current load is supplied with power through the first direct current output power supply; when the external alternating current power supply interrupts power supply, the direct current load is supplied with power through the second direct current output power supply.