In order to study the changes of nutrition and flavor characteristics of fresh Tremella fuciformis before and after hot air drying, the basic nutrients, bioactive components, amino acids and mineral elements in fresh and dried T. fuciformis were comparatively measured. The flavor characteristics of fresh and dried T. fuciformis samples were analyzed by gas chromatography-ion mobility spectroscopy (GC-IMS) and gas chromatography-mass spectrometer (GC-MS). The results showed that the contents of crude protein, crude fat, total amino acids, crude polysaccharides, total polyphenols and total triterpenes in fresh T. fuciformis were significantly reduced after hot air drying (P<0.05). The amino acid content and composition of T. fuciformis changed after air drying, and the amino acid nutritional value of fresh T. fuciformis was closer to the WHO/FAO recommended model of protein. In addition, the contents of some mineral elements such as calcium, iron, copper and zinc in T. fuciformis were reduced after drying. A total of 30 volatile flavor compounds both in fresh and dried T. fuciformis were identified by GC-IMS, and 41 volatile flavor compounds were identified by GC-MS. The composition and content of volatile compounds in fresh and dried T. fuciformis were significantly different. Compared with dried T. fuciformis, fresh T. fuciformis was not only rich in 1-octen-3-ol with typical mushroom flavor, but also rich in α-pinene, ethyl propionate methyl butyrate and other esters with fruity flavor. It could be concluded that T. fuciformis was rich in nutrition and unique in flavor. The research results could provide a certain preliminary theoretical basis for the sales and deep processing of fresh T. fuciformis.