an ion - conducting membrane used in the chlor - alkali industry and a preparation method thereof are disclosed . the ion - conducting membrane includes a perfluorinated ion exchange resin base film , a porous reinforcing material and a perfluorinated ion exchange resin micro - particle surface layer . the perfluorinated ion exchange resin micro - particles are a mixture of one or two of perfluorocarboxylic acid resin micro - particles and perfluorosulfonic acid carboxylic acid copolymer resin micro - particles with perfluorosulfonic acid resin micro - particles . a mass percentage of perfluorosulfonic acid resin micro - particles in the mixture is 50 - 95 %. the surface layer of the present invention has good compatibility and adhesion , and maintains a good degassing effect during the entire lifespan of the ion - conducting membrane . the present invention is used in the chlor - alkali industry , stably and effectively processes alkali metal chloride solutions having a wide range concentration and suitable for operating in a zero polar distance electrolytic cell under novel high current density conditions .