Partially deacetylated chitin nano-fiber (DAChN) dispersions were prepared using mechanical treatment of partially deacetylated crab shell α-chitin under acidic conditions mediated by various protonic acids. The representative organic acids had a better efficiency in terms of mediating the nanofibrillation of chitin fibers in comparison to the inorganic acid (HCl). The DAChN dispersed in water at a pH of 3.5 mediated by gluconic acid exhibited the highest yield of nano-fibers (88.6%), followed by succinic, itaconic, and ascorbic acids with a nano-fiber yield of 79.9%, 73.3% and 66.0%, respectively. The pH, conductivity, viscosity, and light transmittance of dispersions were assessed under different storage times. All of the tested DAChN dispersions were stable for at least 15 weeks at 4℃.