Novel zwitterionic chitin nanofibers (ChNFs) decorated with both cationic (NH₃⁺) and anionic (COO⁻) groups on the surface have broad applications in various environments. Herein, we demonstrate a rapid and high-yield (up to 85%) synthesis of a zwitterionic ChNF by the combination of partial deacetylation and oxidation using the TEMPO/NaClO₂/NaClO system. Meanwhile, we present the potential application of a bio-based ChNF as an environmentally and doubly pH-responsive Pickering emulsifier to replace conventional pH-responsive Pickering emulsifiers such as inorganic nanoparticles or grafted polymers. This high yield preparation achieved by our method will be in favor of the large-scale applications of ChNFs.