Abstract <p>Carbon fiber is widely regarded as one of the most advanced reinforcing materials for high-performance polymer composites, where its dispersibility within the matrix critically influences the mechanical, thermal, and electrical properties of the resulting materials. Although recently progress has been achieved in the dispersion of carbon fiber and the application in energy and environment engineering, there is a limited number of comprehensive reviews to help understand the relationship between the dispersion characteristics of carbon fiber and the properties of carbon fiber-based composites. This paper is focus on the dispersion of carbon fiber in various dispersants and polymer matrix, as well as its applications in mechanic, energy, and environment engineering. The impacts of physical (mechanical stirring and ultrasonic treatment) and chemical (surface modification and dispersants addition) dispersion methods on the carbon fiber dispersibility, morphology, and microstructure, as well as on the mechanical strength, energy storage and conversion, and environmental management of carbon fiber-reinforced composites are critically discussed. In addition, the&#xa0;emerging trends in dispersion technology are summarized, including challenges and opportunities associated with long carbon fiber dispersion, the development of novel dispersants, hybrid dispersion strategies, and surface functionalization. These insights aim to facilitate the broader and more effective application of carbon fiber-based materials across mechanical, energy, and environmental engineering.</p> Graphical Abstract <p></p>