The current infrastructure and technology system of the Internet are facing major challenges in terms of intelligence, diversification, personalization, robustness, and efficiency. It is urgent to change the network infrastructure and build a polymorphic definable and intelligent network. This paper studies and judges the development trend of network technologies in China and abroad, proposes the development goal of polymorphic definable and intelligent network, and extracts a list of key cutting-edge technologies for foresight. Based on these, the development roadmap of polymorphic definable and intelligent network in China for 2035 is constructed. China should prospect the research and development of key technologies including network architecture, addressing and routing, full-dimensional definability, network intelligence, and network robust control, and guide the development of relevant industries through the key contents including core chips, products, and systems. Demonstration projects can be deployed to promote the implementation of intelligent network business, including projects concerning information infrastructure, vertical industry network, space–earth integrated network, ubiquitous interconnection of human and things. In addition, this paper proposes some suggestions on the guarantee measures of polymorphic definable and intelligent network in China from the aspects of policy guarantee, scientific research platform support and joint research, international communication expansion, and human resource cultivation and employment.