Activated alumina has much micro-paths, so the specific surface is large. It can be used as adsorbent, desiccant, defluorinating agent and catalyst carrier. It is also a kind of trace water desiccant and the pole-molecular adsorbent, according to the adsorbed molecular polarization, the attachment force is strong for water, oxide, acetic acid, alkali etc. Activated alumina is high strength, low abrasion, no soften in water, no expansion, no powdery, no crack. It can widely used in the deep drying of cracked gas, ethylene and propylene, hydrogen-generation, air separation, instrument air drying and fluorine treatment for H2O2, also in the adsorbing pollution material, such as H₂S, SO₂, HF and paraffin in the water gas, especially in the drinking water defluorination.