Silica gel is the product of silicon dioxide hydrosol after condensation polymerization, aging and being partially dehydrated. In silica gel, water has three states: free water; water physically adhered on surface and capillary condensation water in micropores; chemical water (existed as silanol group). Capillary condensation water will occupy the adsorption space and decrease the content of free water. However, chemical water which is in the state of silanol group must influence the surface characteristics of silica gel. Thereby, the state of water in silica gel must influence the adsorption capacity of silica gel. The state of water in silica gel depends on its temperature so that the water content in different states can be measured through weighing weight lost of silica gel at different temperatures.