Deionized water equipment is an ion exchange system. Ion exchange system is a traditional water treatment process in which various anions and cations in water are replaced by anion and cation exchange resins. Anion and cation exchange resins are matched according to different proportions to form ion exchange cation bed system, ion exchange anion bed system and ion exchange mixed bed system, The mixed bed system is usually used as a terminal process for preparing ultrapure water and high-purity water after water treatment processes such as reverse osmosis. It is one of the irreplaceable means for preparing ultrapure water and high-purity water.