To explore the drying characteristics and moisture migration and diffusion characteristics of apricot slices in the microwave freeze-drying process of ultrasonic pretreatment, microwave vacuum-freeze drying technology was selected, and the transverse relaxation time T2 inversion spectra of apricot slices during MFD drying under different ultrasonic pretreatment conditions were measured by low field nuclear magnetic resonance. The results showed that ultrasonic pretreatment had a great influence on the drying rate of apricot slices in the early stage of MFD. Scanning electron microscopy showed that the best ultrasonic treatment condition for internal structure was 350 W, 35 ℃, 15 min, and it was beneficial to the transfer of water. Free water in fresh apricots was found accounting for about 83% of the total water. Based on the analysis of the law of water transfer in different flow states during MFD drying of fresh apricot slices, it was concluded that, with the drying process, part of the free water first migrated to the direction of bound water, meanwhile, weakly bound water gradually migrated to bound water, and the migration of combined water to non-mobile water ran through the whole drying process. The effective water diffusion coefficient of apricot slices during drying under different ultrasonic pretreatment conditions ranged from 8.44×10^-11 to 15.00×10^-11 m²/s. Ultrasonic treatment increased the effective water diffusion coefficient of apricot tablets by 82.29%~223.97%.