Ultrasound-assisted thawing has been an innovative and efficient method. To explore the temperature distribution and thawing time of ultrasonic-assisted thawing process， in this paper， an unsteady mathematical model was established to simulate the heat transfer process of ultrasound-assisted thawing by using finite element-based commercial software COMSOL. Results showed that the RMSE was 0.393 ℃ in the ultrasound-assisted thawing process， in the control RMSE was 1.192 ℃. It proved that this model agrees with the experiment well. At the same time， ultrasound-assisted thawing can significantly improve the thawing rate， thawing time was reduces by 30.9% compared to the control. Based on the good prediction of model， we investigated the influence of several design parameters on the thawing effects. With the increase of the radius and height of potato， thawing time increased， but there was no linear relationship between temperature difference and size. The position of potato in the sound field also had great influence on the thawing effect. When the distance between the upper surface of potato and ultrasound probe was 65mm， the thawing time and temperature difference were the least. Therefore， in order to achieve the best thawing effect， it is necessary for us to consider the specific conditions to optimize the best size and placement position.