As the progressive development of intelligent substation technology, the importance of communication technology is more and more obvious, and the communication network reliability has been the focus of attention. The article firstly describes communication network structure in the intelligent substation, and then the analysis of the communication reliability problems in substation are given. From the point of view of second-layer switching technology, through the VLAN, Ring, QoS, multicast, and other technical details, each scheme of technical application is provided according to various features of IED and business data flow characteristics Also some experiments are carried out to verify the communication reliability. So, flexible use of these reliability technologies, and reasonable design of network topology, can support secure, stable and reliable transmission of communication message in intelligent substation, therefore the whole substation will become more and more strong.