A mobile network-based tenant network service implementation method and system and network elements are disclosed. The method includes: an MME of a mobile network performing identity authentication of a tenant network to which UE belongs on the UE; after the UE passes the identity authentication of tenant network, the MME selecting a local exchange node for the UE; the MME transmitting a creation/update message of a local exchange forwarding table to the local exchange node; the local exchange node creating or updating the local exchange forwarding table and generating a forwarding table entry of UE, wherein the forwarding table entry comprises identification information of UE; after UE bearers establishment are completed, the local exchange node writing UE bearer information into the forwarding table entry of UE; and the local exchange node implementing message forwarding of the tenant network according to the local forwarding table, thereby implementing a tenant network service.