Fuente: Wipo "IOT" The invention relates to a NB-IoT fixed terminal and a vehicle-mounted mobile NB-IoT system, which comprise that the NB-IoT fixed terminal determines a coverage level, does not attach to a base station with a low coverage level when the coverage level is low, and waits for the mobile NB-IoT base station; the NB-IoT mobile base station establishes a connection with the NB-IoT fixed terminal and negotiates TAU time, and when the connection with the NB-IoT fixed terminal is not successfully established, the identifier of the NB-IoT mobile terminal is changed into the identifier of the NB-IoT fixed terminal. In the application, the NB-IoT fixed terminal is not attached to the low-coverage-level base station, so that excessive power consumption under the low coverage level is avoided; and whenthe NB-IoT mobile base station does not successfully establish connection with the NB-IoT fixed terminal, the NB-IoT mobile terminal changes to the identifier of the NB-IoT fixed terminal and accessesthe network to maintain registration of the NB-IoT fixed terminal in the core network.