Carbon fiber has attracted widespread attention due to its exceptional thermal, electrical, and mechanical properties. Here, the initial part is the polymerization reaction mechanisms and molecular structure design, along with key developments in spinning processes, whereby a theoretical foundation is laid for the controllable production of high-performance carbon fiber. In the field of composite interfaces, the chapter focuses on the overall performance of composites through molecular design of sizing agents and in-depth analysis of fiber-resin interfacial control mechanisms, while also expanding into the development of antibacterial functional materials. Innovation in multifunctional composites is further pursued, resulting in the successful development of continuous manufacture of carbon fiber paper and breakthroughs in precise structural control technology for carbon aerogels. At the application level, the industrial implementation of carbon fiber materials in the energy sector is actively promoted, including their use in hydrogen fuel cells, advanced battery technologies, and supercapacitors. Meanwhile, studies on carbon felt applications in environmental adsorption functional materials and extreme-environment thermal protection materials provide effective material solutions for addressing energy and environmental challenges. Overall, the research reflects a deep integration of fundamental theoretical innovation and engineering application practices, driving transformative advancements in the high-end manufacturing sector of carbon fiber and its composites.