The invention discloses a SDN (Software-Defined Networking) inter-domain routing implementation method. In the SDN inter-domain routing implementation method, a controller of an SDN autonomous domain undertakes an inter-domain routing function and is responsible for interacting BGP routing information with a controller in an adjacent SDN autonomous domain, generating an optimal path based on a routing strategy of the autonomous domain thereof and informing neighbor autonomous domains of the path. The controller of the SDN autonomous domain realizes an interactive interface of an OpenFlow protocol and a BGP protocol, calculates to obtain an updated table item of an OpenFlow switch flow table in the domain based on the generated optimal path and intra-domain topological information, and sends the flow table item to an appointed switch to realize routing strategy thereof. The SDN inter-domain routing implementation method disclosed by the invention has the advantages that the BGP protocol can be applied to the SDN inter-domain routing under the precondition of not damaging the existing SDN network structure, and the protocol interactive interface is designed for the controller to help the controller to realize the routing strategy.