A method for efficiently and uniformly dehydrating carrot through high and low frequency microwave combined pulse spray drying belongs to the technical field of fruit and vegetable food processing. The method comprises the steps of carrot selection, cleaning and peeling, slicing, 2450 MHz and 915 MHz microwave combined pulse spray drying and nitrogen-filled packing. The sequence of two microwaves at different frequencies is interchangeable. When 2450 MHz drying is performed before 915 MHz drying, the dry basic water content of sliced carrot can be reduced to be less than 0.15g/g, compared with common hot air drying, the drying time can be shortened by about 30%, and compared with common microwave drying, the drying uniformity can be improved, the non-uniformity can be reduced by 70%, the content preserving rate of beta-carotene reaches 77%, and the rehydration ratio reaches 3.24; when the 2450 MHz drying is performed after the 915 MHz drying, the dry basic water content of the sliced carrot can be reduced to be less than 0.15g/g, compared with the common hot air drying, the drying time can be shortened by about 40%, and compared with the common microwave drying, the drying uniformity can be improved, the non-uniformity can be reduced by 50%, the content preserving rate of beta-carotene reaches 65%, and the rehydration ratio reaches 2.84; both enhance the comprehensive produce quality.