Abstract: In order to explore the effect of hydrophobic groups and particle size of octenyl succinate anhydride corn starch (OSACS) on the stability of Pickering emulsion, the study analyzed the physical and chemical properties of OSACS hydrolyzed by hydrochloric acid and the stability of Pickering emulsion. OSACS was prepared from corn starch and octenyl succinate anhydride (OSA) in aqueous slurry systems. OSACS was hydrolyzed by 1 mol/L hydrochloric acid for different times (1 d, 2 d, 3 d, 4 d, 5 d) to different degrees, then was formed to Pickering emulsions with soybean oil and water. The physical and chemical properties of hydrochloric acid hydrolyzed OSACS and the properties of particle-stabilized Pickering emulsion were investigated by scanning electron microscope, laser particle size distributor, fourier transform infrared spectrometer, differential scanning calorimeter, microscope and rheometer. With the prolongation of acid hydrolysis time, the results showed that the substitution degree of OSACS decreased from 0.0203 to undetectable, gelatinization temperature decreased from 67.38 ℃ to 56.19 ℃, the peak intensity of IR spectra at wavelengths of 1750 cm^-1 and 1574 cm^-1 was weakened, the average particle size decreased from 18.09 μm to 6.22 μm, and the crystallinity increased from 19.98% to 25.91%. OSACS with a degree of substitution of 0.020 3 could form stable emulsions with small droplet size. The rheological properties of emulsions showed that all emulsions had shear thinning properties. The storage modulus of OSACS emulsion was higher than that of hydrochloric acid hydrolyzed OSACS and the storage moduli of emulsions were greater than the loss moduli. It was indicated that the Pickering emulsions stabilized by OSACS particles were elastic and had properties similar to viscoelastic weak gel. The results showed that within the change of particle size at micron level, the decrease of particle size had no significant effect on the stability of Pickering emulsion, while the OSA groups played a dominant role in the stability of Pickering emulsion. The results will provide reference for the study and application of OSACS in Pickering emulsion.