Abstract: The process conditions of ultrasonic modifying rice bran protein was optimized, taking solubility, emulsifying activity and emulsion stability as indicators. The microcapsulated powder oil was prepared via spray drying process using modified protein and maltodextrin as the wall materials, flaxseed oil as the core material. Besides, the effects of modified protein on its encapsulation efficiency, particle size, zeta-potential and microstructure were studied. Results indicated that the highest solubility, emulsifying activity and emulsion stability of rice bran protein were achieved with 4 g/100 mL of protein after 30 min of ultrasound treatment with power density of 5 W/mL, being 79.04%, 19.97 m²/g and 168.2 min, respectively. The protein structure was partially expanded and the emulsbility was improved, which were illustrated by a decrease in the content of disulfide bond by 38.68%, and an increase of surface hydrophobicity by 65.11%. Moreover, higher encapsulation rate of 75.52% was obtained with the powdered-oil containing ultrasonic-modified protein. The particle size distribution was shifted to the left, while the average particle size decreased after reconstitution. Futhermore, the emulsion stability was improved by preventing the aggregation of oil droplets with a higher zeta-potential. The SEM image showed that surface of this powdered-oil was smooth, and the particles were small without severe rupture on the surface. The β-turn content of ultrasonic-modified protein in powdered-oil increased and the protein was stretched and restructured, which enhanced the molecular flexibility and finally resulted in better emulsifying property. This laid the foundation for the development of novol materials for microcapsules.