Disclosed is a direct current uninterruptible power supply system. The direct current uninterruptible power supply system according to an embodiment of the present invention is electrically connected to a direct current power converter for converting commercial alternating current power to direct current power, in order to: supply the direct current power to a load and charge an auxiliary power supply device therein with the direct current power. In the case of a short circuit of the direct current power converter due to a current leakage or breakage of the direct current power converter, or if the direct current power converter is disconnected, the direct current uninterruptible power supply system enables the auxiliary power supply device to constantly supply power to the load while completely blocking the electrical connection to the direct current power converter.