Chitin nanofiber (ChNF) has attracted much attention in biomass materials because of its high aspect ratio, high specific surface area, low density and rich functional groups. Chitin mainly comes from shells of crustaceans such as crabs and shrimps, squid parietal bones and cell walls of fungal plants such as mushrooms. In recent years, the surface modification of chitin and its applications in food, chemical and other fields have been reviewed. However, the summary of nano- preparation of chitin and functional application of chitin nanofibers in production technology and comprehensive performance needs to be further improved. In this paper, the research progress of extraction methods, nano- preparation technology and functional applications of chitin nanofibers in organisms were reviewed. Optical transparent materials, high-strength gel materials, high-strength silk threads, degradable packaging materials made from chitin nanofibers, composite materials with chitin nanofibers as reinforcing phase and their applications in biomass material fields such as flexible display, flexible sensing, intelligent packaging, biomedicine, tissue engineering and degradable packaging were introduced. Finally, the future research directions of the preparation and functional applications of chitin nanofibers were prospected, in order to provide reference for later researchers to develop new functional chitin nanofibers.