The invention belongs to the technical field of snack food processing, in particular to instant tremella crisp snack food, and further discloses a preparation method thereof. The instant tremella crisp snack food is prepared from tremella as a main raw material by steps of boiling of fresh tremella in boiling water, low-frequency ultrasonic pretreatment and vacuum freezing in series with microwavevacuum drying. The instant tremella crisp snack food completely retains nutritional components of the tremella, has crisp and pleasant taste and strong palatability, is convenient to carry and storefor a long time, and is the novel tremella snack food which is instant, nutritional and good in sensory property, the novel healthy tremella snack food is developed, and the audience range and marketapplication of tremella food are effectively expanded.