With the aim to improve the efficiency of hot-air drying, a dryer of hot-air drying combined power ultrasound was explored according to the advantages of ultrasound on enhancing heat and mass transfer and the acoustic impedance of flexural vibrating plate. In this dryer, ultrasound could work effectively in air. The results of mushroom slices drying showed that the drying time using hot-air drying combined power ultrasound at 20kHz, 150W and diameter 20cm plate was shorter as 50% as that using hot-air drying and the energy consumption per kilogram of water evaporation reduced by 22%. The mechanism of ultrasound which enhanced hot-air drying was discussed. It was possible attributed to ultrasound mechanical actions to enhance the moisture diffusion controlling step in the drying processing.