In a relay managing method through a network management system (NMS) server, a registration request is received from a relay BTS interface unit (BIU). The identification information of the BIU that transmits the registration request is compared with a previously registered BIU registration table, and a new BIU ID is provided to the BIU that transmits the registration request, when information corresponding to the identification information of the BIU that transmits the registration request does not exist in the BIU registration table. Subsequently, registration is performed by mapping the identification information of the BIU that transmits the registration request and allocation IP information to the provided new BIU ID.