Abstract: Lignin, as the most abundant aromatic compound in nature, has a carbon content of 30%-40% and is a high-quality raw material for preparing carbon fiber. However, due to the characteristics of amorphous chemical structure, low molecular weight, wide molecular weight distribution and poor arrangement, its complex heterogeneous structure and inherent flocculation characteristics need to be overcome by modification. In this paper, the basic structural units and characteristics of lignin were introduced, and on this basis, the modification process conditions such as physical mixing, chemical modification and biological action were described in detail, and their effects on the lignin structure and the strength, electrochemistry, filtration and air permeability of lignin-based carbon fibers were also described. On this basis, the application of carbon fiber in the fields of transportation, construction, aerospace, life and health and new energy was discussed. In addition, the feasibility of directional functional group modification, green modification method and modification process expression of lignin were summarized, which provided thinking for further research and development of lignin-based carbon fiber composites and promoted their industrial application.