The invention relates to a method for uniformly drying agaricus bisporus slices through variable-frequency ultrasound-assisted impregnation pretreatment and vacuum microwaves, and belongs to the field of deep processing of agricultural products. The method comprises the following steps: cleaning agaricus bisporus and cutting into 5-8mm thick slices, protecting color by using a mixed solution of vitamin C, citric acid and calcium chloride, and carrying out variable-frequency staged ultrasound impregnation treatment on the color-protected agaricus bisporus slices: a first stage: putting the agaricus bisporus slices in clear water according to a ratio of agaricus bisporus slice to water of 1:5, and setting the water temperature to 45-50 DEG C, the ultrasonic frequency to 45KHz, the ultrasonic power to 120-150W, and the treatment time to 30-40min; a second stage: taking out the agaricus bisporus slices and putting into a mixed solution of 50-60% by mass fraction of sucrose and 5% by mass fraction of salt according to a ratio of agaricus bisporus slice to mixed solution of 1:10, and setting the water temperature to 35-40 DEG C, the ultrasonic frequency to 100KHz, the ultrasonic power to 210-240W and the treatment time to 40-50min; finally, carrying out vacuum microwave drying, and setting the microwave transmitting power to 15-20W / g, the degree of vacuum to 70-80kPa and the drying time to 15-25min. The agaricus bisporus slices subjected to variable-frequency ultrasound-assisted impregnation treatment has uniformly distributed dielectrics; when the vacuum microwave drying is carried out, a material is uniformly heated in a microwave field, and moisture is rapidly evaporated, so that the dried agaricus bisporus slice is uniformly distributed in color and luster, and is uniform in shape and better in rehydration.