The present document provides a method, a device and a system for implementing a local gateway service. Wherein the method includes: adding, by a first connection device, a second connection device for a terminal (300); interacting collocated local gateway address information between the first connection device and the second connection device (301); and reporting, by the first connection device, determined collocated local gateway address information to a core network, and using, by the core network, the collocated local gateway address information to perform the local gateway service (302). Through the technical solution provided by the embodiment of the present document, the core network obtains the collocated local gateway address information, and the local gateway service is implemented aiming at a dual-connection service scenario.