Drying the yeast cells into a dormant state, that is, preparing solid active dry yeast, and the active dry yeast is convenient for transport and storage, and widely used in the fields of wine making, baking, biological control and so on. During the process of preparing active dry yeast, drying the yeast is an important step. It was introduced that the thermal drying methods, including drying methods of using vacuum, spray, and fluidized bed, which are economical, high in feasibility, low energy consumption, and can be preserve for a long time. Moreover, the factors affect the activity of dry yeast during the whole drying process were also analyzed, including the tolerance of the yeast to the external environment, the culture conditions of the yeast, the addition of the protective agent, the drying process, the storage and rehydration conditions, etc. finally, the methods to improve the activity of the yeast were discussed.