The invention discloses a conventional IP network and SPTN network intercommunication method and system. The method comprises the steps that path information and topological information in an SPTN domain are collected; a BGP neighbor is established for a conventional IP network and an SPTN network; the conventional IP network transmits a BGP message to a first-stage control unit to realize message intercommunication of the SPTN network and the conventional IP network; boundary information of the boundary routers of the conventional IP network and boundary forwarding equipment of the SPTN domain is collected; paths between all the boundary nodes of the SPTN network are established, flow table items on the routes are generated, and the generated flow table items are issued to an SPTN data plane; and when data packets come, data forwarding is performed according to the flow table matching situation. The system comprises a topological collection device, an initialization device, an ARP proxy device, an information management device, a routing protocol processing device and a link management device. The conventional IP network is enabled to seamlessly intercommunicate with the SPTN network without influencing original IP network route planning so that network application opening of the SPTN network is facilitated without influencing implementing of existing business.