The present invention discloses through edge media gateway realizing IP cross domain intercommunication system. Said system includes adjacent heterogenous or homogeneity IP domain, each IP domain including media gateway controller used for call control; gateway used for media bearing; using single edge media gateway in adjacent heterogenous or homogeneity IP domain realizing cross domain intercommunication. The present invention also provides realizing IP cross domain intercommunication method; when different domain media calling media gateway communicate with called media gateway, calling media gateway makes calling junction and media stream establishment between edge media gateway and called media gateway under controlling by respective media gateway controller; calling media gateway and called media gateway to make cross-domain communication based on established media stream. The present invention can realize two different IP network communications through single edge media gateway.