Silica gel desiccants are different varieties of silica gel packed in small bags with moisture permeability. The main raw material silica gel is a kind of silica with high microporous structure containing water, non-toxic, tasteless, odorless, stable chemical properties, with strong hygroscopicity, is a kind of highly active adsorption material. It is usually prepared by reaction of sodium silicate and sulfuric acid and by a series of post-treatment processes such as aging and acid bubble. Silica gel belongs to amorphous material, its shape is transparent and irregular sphere, its chemical formula is mSiO2·nH2O. Therefore, it is widely used to control the relative humidity of the environment in the storage and transportation of instruments, meters, equipment and instruments, leather, bags, shoes, textiles, food, medicines, etc., so as to prevent the articles from being affected by damp, mildew and rust.