Chitin nanocrystals (ChN) with different crystallinity index values were obtained by acid hydrolysis method, and O/W type Pickering emulsion was prepared by homogeneous synergistic ultrasonic technology. The crystallinity index values and functional groups of chitin nanoparticles were calculated and analyzed by X-ray diffraction and Fourier infrared spectroscopy. The microstructure, interfacial contact angle, thermal stability, physical stability, creaming stability and storage stability of the emulsion were determined. The effect of different crystallinity index values of ChN on emulsion stability was analyzed. Result showed that acid hydrolysis did not destroy the chitin functional group, but acid hydrolysis can change the crystallinity index values of chitin, and the crystallinity index values of ChN obtained at the acid hydrolysis of 2.5h was the largest, which was 78.15%;the emulsion prepared by ChN with high crystallinity index values formed a more stable network structure, and ChN was more attached to the oil-water interface, so that the emulsion had a smaller interface contact angle and increased the hydrophilicity of the emulsion;it was also found that the ChN stable emulsion with high crystallinity index values had good thermal stability index and physical stability index, which were 63% and 69.52%, respectively;the emulsion analysis stability was good, and the emulsification index was less than 1%. In addition, the ChN-stabilized emulsion did not stratify after storage for 30 days at room temperature, and had good storage stability, and the emulsion with the highest crystallinity index values had the smallest particle size. Therefore, a stable O/W Pickering emulsion can be prepared by increasing the crystallinity index values of the chitin nanocrystals.