In recent years increasing demands for consumption of seafood leads to an increase in production of huge amount of waste. In thThe purpose of this research was extracting chitin from shrimp shells and application of acidicand mechanical treatments for production of chitin nanocrystal. Chitin is one of the most abundant semi-crystalline polysaccharides in nature. By removing amorphous regions under specific terms, nanocrystals are formed. Due to the different benefits of nanocrystal chitin, including easy access, non-toxicity, biodegradability and low density,, their use in various fields of the food industry has attracted the attention of researchers. In this research, for the production of chitin nanocrystals, pure chitin was first extracted by alkaline treatments to remove protein, acidic treatments for removal of minerals, and then bleaching. Acid hydrolysis with hydrochloric acid was used at different times (60, 120 and 180 min) at 80 ° C under hydrothermal conditions and nanocrystals with the highest degree of crystallinity were produced. Hydrochloric acid concentration of 3 M for 120 minutes was selected as the optimum conditions for the production of chitin nanocrystals with a degree of crystallinity of 88%. Also, to investigate the effect of the mechanical stage on the properties of nanocrystals, ultrasonic process in different powers and times were used. The images obtained from scanning electron microscopy showed that optimum conditions for the production of nanoparticles were using ultrasonic power of 300 and a time of 4 minutes. The images of transmitted electron microscopes represent the production of spherical nanoparticles with a size of 49.7 nm. Results of Fourier transform infrared spectroscopy indicated removal of proteins and minerals, maintaining the structure of chitin in all treatments and increasing the degree of crystallinity. The present data from differential scanning calorimetry showed that produced nanocrystals exhibited less resistance to the destruction of crystalline structure than pure chitin. The charts of thermal weights indicated the reduction of the chitin stability nanocrystals after acid and alkaline treatments against fragmentation. Nanocrystalline chitin was used to stabilize 10% oil-in-water emulsion. The results showed that with increasing nanocrystal chitin concentration (0.1 to 1.5%), the stability of the emulsions increases to heat, stress and storage time. In order to investigate the size of oil particles in emulsions with different concentrations of nanocrystals, an optical microscope was used which showed that increasing the concentration of nano-crystals decreases the size of the oil droplets. It was also found that a stabilized emulsion by chitin nanocrystal had lower oil particles and more stability during storage in comparison to emulsion stabilized with similar concentration of lecithin.. Keywords : Chitin Nanocrystal, Emulsion, Suspension, Ultrasonic, Acid Hydrolysis