In order to solve the standing wave problem generated by single-frequency ultrasound, the whole egg liquid was dried by double-frequency ultrasonic vacuum. The mechanism of dual-frequency ultrasound was studied. The digital simulation results showed that under other conditions, dual-frequency ultrasound had better cavitation effect than single-frequency ultrasound. Compared with single-frequency ultrasound, when using double-frequency ultrasonic drying of whole egg liquid, the drying time was shortened by 30%, the average drying rate was increased by 41.6%, and the effective diffusion coefficient of water was increased by one times, which showed that dual-frequency ultrasound was beneficial to shorten the drying time of materials, increase the drying rate, and thus improving energy efficiency. Low field nuclear magnetic resonance and magnetic resonance imaging techniques were used to analyze the effects of single-frequency and dual-frequency ultrasound on internal water state and migration during whole egg liquid drying. The results showed that with dual-frequency ultrasound, the change of the overall peak area on the inversion spectrum was more significant than that of single-frequency ultrasound, indicating that dual-frequency ultrasound was beneficial to improve the fluidity of the water in the material and was more conducive to drying. In the initial stage of drying, the amplitude of the signal corresponding to free water in the inversion spectrum was gradually reduced, and the transverse relaxation time was gradually shortened. In the middle and late stages of drying, with the large amount of free water removed, the drying was mainly to remove the combined water and semi-bound water. The results of magnetic resonance imaging showed that the dual-frequency ultrasonic drying had lower brightness than the single-frequency ultrasonic drying H+ proton density image during the same time period, indicating that dual-frequency ultrasound was more likely to promote the internal moisture removal of whole egg liquid.