To explore the moisture migration law of Dioscorea opposita in contact ultrasound enhanced heat pump drying， this paper used the contact ultrasound enhanced heat pump drying equipment to study the effect of ultrasonic power on drying characteristics and water change. The results showed that applying contact ultrasound during the heat pump drying was beneficial to accelerating the dehydration process. With the increase of ultrasonic power， the drying time of Dioscorea opposita could be shortened from 630 min to 390 min， and the average drying rate could be increased from 0.0053 g/(g·min) to 0.0086 g/(g·min)， the range of effective moisture diffusion coefficients was increased from 0.887×10-10 m2/s to 1.393×10-10 m2/s. Scanning electron microscopy results showed that contact ultrasound could loosen the material structure and produce micropores. With the increase of ultrasonic power， the number of micropores increased and the porosity increased. Low-field nuclear magnetic resonance analysis showed that there were three kinds of moisture in Dioscorea opposita: free water， immobilized water， and bound water. There was mutual migration of internal moisture during the contact ultrasound enhanced heat pump drying process. The content of free water decreased continuously until it was completely removed. The content of immobilized water first increased and then decreased in the drying process， and there was still some immobilized water existence at the end of drying. The content of bound water was almost unchanged during the drying process. The nuclear magnetic resonance imaging of Dioscorea opposita showed that the moisture of the material gradually lost from outside to inside during the drying process. Increasing ultrasonic power during the drying process could accelerate the internal moisture migration rate of Dioscorea opposita and promote the removal of internal moisture. This study could provide a reference for the development and application of contact ultrasound enhanced heat pump drying technology for fruits and vegetables.