The invention discloses a processing method for dehydrating toadstool. The method comprises the following steps: A, selecting materials; B, washing; C, blanching; D, cooling; and E, protecting color,namely soaking toadstool at normal temperature, with a color fixative which is mixed by phytic acid, citric acid, vitamin C, edible salt, edible glucose and water; F, draining; G, freezing, namely freezing the drained toadstool at negative 20-negative 30 DEG C; H, lyophilizing with microwave, namely starting a microwave source at a vacuum degree of 65-125pa, and dehydrating with microwave; and I,packaging. According to the method, a microwave lyophilizing drying process is adopted, the dehydrating and drying time can be shortened, and the problem of slightly high content of moisture inside toadstool in a traditional drying process can be solved; and the moisture content of toadstool is less than 5 percent when the drying method is adopted, so that long-time preservation can be facilitated, and nutritional ingredients are slightly lost. The color fixative adopted in the processing method has low content of sulfur dioxide, and is harmless to body health.