In this study, ultrasonic and vacuum freeze drying were combined to dry yogurt. Compared with the vacuum freeze drying, the effects of ultrasonic time, power, and pulse on water evaporation and drying time of yogurt were determined. Meanwhile, the drying kinetics model was established. The results showed that the ultrasonic synergistic vacuum freeze drying, significantly improving moisture diffusion of the material under the conditions of the low air velocity and low temperature, could shorten the total drying time. The optimal drying conditions were ultrasonic power 495W (55%), ultrasonic pulse 5∶3, and ultrasonic time 1.5h. Compared with the control group, the total drying time under the optimal conditions decreased 20.58h. Moreover, the drying kinetics model was W_t=W₀e-Kt.