The ionic membrane caustic soda from whole bittern has strict requirements for the quality of brine entering the electrolyzer. If the unqualified brine enters the ion membrane electrolyzers, the impurity ions in the brine react with hydroxide and other hydroxides to form insoluble precipitate and block the micropores of the membrane. It will lead to a decrease in the exchange performance of the ion membrane, an increase in the cell voltage, and a decrease in the current efficiency, which greatly increases the cost of caustic soda and reduces the economic benefits. Our brine iodine removal process can adsorb the iodine in the brine to make its content less than 0.1 mg/L that effectively avoid the deposition of iodate and periodate on the ion membrane, reduce the replacement frequency of the ion membrane, and maintain a good comprehensive operation efficiency.