Abstract:At present，milk is mainly sterilized by heat treatment，which，however，will deteriorate the quality of milk to varying degrees. Ultrasonic treatment can retain the nutrients in low-lactose milk. Low-lactose milk was subjected to ultrasonic treatment，and the effects of different ultrasonic power （100，150，200，and 250 W）and ultrasonic time （5，10，15，and 20 min） on the quality of low-lactose milk stored at 4 ℃ for 21 days were studied with acidity and pH as indicators. The results showed that the optimal sterilization conditions were ultrasonic treatment at 150 W for 10 min. The storage test showed that low-lactose milk could be preserved for about 15 d after ultrasonic treatment，while fresh milk and low-lactose milk without ultrasonic sterilization could only be preserved for about 6 d. The stability test during the storage period showed that the low-lactose milk could be stored for 15 d under 4 ℃，with negative result in the alcohol test，no rancidity or fat stratification，and it still maintained good quality after storage for 15 d. As the ultrasonic power and ultrasonic time increased within certain ranges，the quality of low-lactose milk was gradually improved due to the emulsification and homogenization effects of ultrasound，which decreased the turbidity and improved the emulsifying properties of low-lactose milk.