Vacuum drying box for the older drying device, the box is divided into several layers by the heating plate. The heating plate is fed with hot water or low pressure steam as the heating medium, and the material plate of the medicine to be dried is placed on the heating plate, the door of the box is closed, and the box is pumped into vacuum by vacuum pump. Heating plate in the heating medium circulation flow will be heated to the specified temperature, the water that is beginning to evaporate and with the vacuum gradually pumped away. This equipment is easy to control, can be condensed to recover the evaporated solvent, drying process is not easy to be contaminated with drugs, can be used in the drying of drugs, packages and heat treatment on the sterilization. In the 1980s, the API industry used this equipment as the main dryer, but because it is not easy to clean the material tray online and online sterilization, drying speed is slow, the labor intensity of workers, and in order to achieve uniformity of drugs, drying but also by the mixing device mixing, now the API large-scale production has been rarely used, more for the pilot production or heat treatment of packages.