The invention provides an online activated direct-current power system. The online activated direct-current power system comprises a system monitoring module and an online activated direct-current power supply, wherein the online activated direct-current power supply comprises a communication control module, a battery activation module and a battery module, the system monitoring module is connected with a direct-current bus, the system monitoring module is used for monitoring the load information of the direct-current bus, generating preset control information according to the load information and sending the preset control information to a to-be-activated communication control module of the online activated direct-current power supply, and the battery module is used for supplying power to the direct-current bus; the battery activation module is electrically connected with the battery module, and used for controlling the disconnection of the battery module and the direct-current bus so as to activate the battery module, the communication control module is electrically connected with the battery activation module, and used for correspondingly controlling the battery activation module to activate the battery module according to the preset control information. The online activated direct-current power system provided by the embodiment of the invention has the characteristics of being high in excitation efficiency, good in power supply stability, low in maintenance cost and the like.