A kind of link monitoring based on the multicast and TCP communication method is proposed to satisfy TCP communication under the architecture of dual network in the dispatch and substation integration system.This method includes monitoring by multicast，smart network interface card（NIC）selecting，judging on real-time status and filtering based on unknown nodes.The monitoring by multicast can mutually monitor the link status by receiving the opponent multicast packet.The smart NIC selection can communicate by selecting the optimal network according to each other's link status and network traffic.The judging on real-time status ensures that communication can be promptly interrupted after a network failure occurs.The filtering based on unknown nodes can actively refuse the communication request of the unknown node initiated outside the system，and ensures the security and stability of an system.The method of link monitoring and TCP communication is able to achieve efficient，safe and reliable TCP communication under the architecture of dual network in dispatch and substation integration system.