A reachability management method and device for a machine-to-machine/man (M2M) terminal/terminal peripheral are provided in the embodiments of the present document, which relates to machine-to-machine/man communications. The reachability management method for the M2M terminal/terminal peripheral provided in the present document includes the following steps: when selecting to switch to an M2M stub network, the M2M terminal/terminal peripheral sending a detach request message to a corresponding network side device, wherein the detach request message comprises a terminal signalling connection retention indication; and meanwhile, the M2M terminal/terminal peripheral sending a registration request message to an M2M gateway, wherein the registration request message contains an identifier of the network side device. A terminal, a network side device and an M2M gateway device are also provided in the embodiments of the present document.