In order to prepare rice bran oil emulsion with better stability, sodium caseinate and rice bran oil were used as raw materials, and ultrasonic treatment was used to study the effects of sodium caseinate addition, lipid/water ratio, and ultrasonic intensity on the preparation of rice bran oil emulsion. The results showed that when the addition amount of casein reached 0.6% (w/w), the protein utilization rate was higher. The protein adsorption capacity of the emulsion reached 90%, and the average particle size of the oil droplets in the emulsion was significantly reduced compared to the sample with 0.5% (w/w). The increase in the ratio of oil significantly increased the viscosity of the rice bran oil emulsion. Observations by optical microscope revealed that the oil droplets in the rice bran oil emulsion with a lipid/water ratio of 3∶2 were densely distributed. When the lipid/water ratio was 3∶2, the emulsifying activity of the emulsion was about 16 m²/g higher than that of the emulsion with a lipid/water of 1∶2. When the protein addition amount reached 0.6% (w/w), the lipid/water ratio was 3∶2, and the ultrasonic intensity was 240~360 W. The sodium caseinate utilization rate of the prepared emulsion is high and the stability was high. Ultrasonic treatment obviously improves the stability of the emulsion, and ultrasonic changes the secondary structure of sodium caseinate, which affects the ratio of β-turn and β-sheet.