Embodiments of the present invention provide a method, a device, and a system for realizing disaster tolerance backup. The method includes the following steps: a device with an active-standby function determines a current state of the device with the active-standby function, after it is determined that the current state is an active state, the device with the active-standby function issues reachable route information to a connected routing device, where the device with the active-standby function and a device of which a current state is a standby state have a same IP address, the reachable route information includes route information relevant to the IP address, so that the IP address is reachable, and the device with the active-standby function and the device of which the current state is the standby state are backup devices for each other. The present invention can realize remote disaster tolerance backup and avoid service interruption.