The invention belongs to the field of food processing, and particularly relates to a preparation method of dried day lily. The dried day lily is prepared by the working procedures of with fresh day lily buds as raw materials, destemming, rinsing by running water, leaching, putting into dishes, carrying out microwave heating for deactivating enzymes, cooling, carrying out once microwave drying for dehydrating, cooling, carrying out secondary microwave drying for dehydrating, cooling, carrying out three-segment far infrared rotary baking, and packaging. According to the invention, microwave heating for deactivation of enzymes for three times, dehydration and three-segment far infrared rotary baking and drying modes are adopted, the day lily is subjected to enzyme deactivation, dehydration and drying, and sterilization, and the prepared dried day lily can be directly eaten or can be eaten after rehydrated. The method provided by the invention is beneficial to preservation of the dried day lily, also keeps the color, fragrance, flavor and shape of the day lily well, and effectively solves the problem of nutritional ingredient loss in the processes of deactivating enzymes and drying. The dried day lily prepared by the method provided by the invention is straight and uniform in shape, is golden yellow and green in color, and can be preserved for 18 months with perfect packages under the normal temperature condition.