The existing problems of communication network in smart substation are analyzed. Based on the development of network communication in smart substation, a high reliability adaptive network technology is developed based on Ethernet Passive Optical Network (EPON) technology (hereinafter referred to as improved EPON technology). The improved EPON technology improves the traditional EPON communication service and Quality of Service (QoS). The network management function is improved by using the Configuration Description File (SCD). By optimizing the network delay measurement scheme, the precise control and traceability of the delay can be realized, and the Parallel Redundant Network (PRP) technology is introduced, in order to meet the demand of smart substation in real-time, usability and reliability. A communication scheme based on improved EPON technology is proposed, the simulation results show that the proposed scheme is suitable for smart substation and has been applied in specific projects. This work is supported by Science and Technology Project of State Grid Corporation of China (No. SGZJ0000 and No. BGJS1600324).