Food freeze-drying is a process of sublimation dehydration and drying of various materials containing moisture under low-temperature freezing and vacuum conditions. It is carried out under the conditions of oxygen-free and light-proof. The thermal denaturation is small and the characteristic flavor of the food is effectively maintained. Food freeze-drying can maximize the preservation of various vitamins, carbohydrates, proteins, chlorophyll, biological enzymes, amino acids and other ingredients in food.