Abstract: Nowadays, China is in a critical period of economic and social transition from rapid development to high-quality development. Advanced information and communication technologies empower traditional industries in energy and transportation.The integrated development of the three networks, i.e., energy network, transportation network, and information network will effectively promote the energy transition and build the powerful transportation country, realizing the green, smart and sustainable development. In this paper, the advantages and demand of the integrated development of the energy network, transportation network and information network are sorted out and analyzed systematically, and the necessity of the integrated development is clarified. The status of the infrastructure construction and the existing technical support for the integrated development of the three networks, and the preliminary attempts in the field of electric vehicle charging services are summarized to discuss the path and the feasibility of the integrated development. The form of the integrated development is analyzed, and the architecture of the integrated system of the three networks is proposed. Moreover, the main characteristics of the integrated system of the three networks are summarized. From the four perspectives of the physical layer, perception layer, platform layer, and application layer of the architecture of the integrated system of the three networks, the key technologies for the development of integrated system are investigated. Finally, the key theories for the integrated analysis of the three networks are discussed.