At the beginning of 1980s, the advanced ionic membrane could operate at the current density of 4000A/m, and the current efficiency was 95% ~ 96%. It can directly produce 35% sodium hydroxide concentration, and the service life of ionic membrane is about 2 years. As the ion membrane method has many advantages, the ion membrane method will be used in the new chlorine - alkali production equipment in the future. Some of the existing mercury or membrane plants will also be converted to ionic membrane when the technology is modified.