A series of quaternary ammonium polysulfone (QAPSU) anion exchange membranes used the chlorotrimethylsilane instead of toxic chloromethyl methyl ether and quaternized-functionalized by trimethylamine ethanol solution were prepared. The effect of chloromethylation reaction time on membrane morphologies and physiochemical properties such as ion exchange capacity, water swelling, and membrane area resistance, mechanical and thermal stabilities was investigated. When being applied in electro-electrodialysis (EED) for purifying phosphoric acid solution, the QAPSU membranes exhibit high purification efficiency, especially all the metal ions (Fe, Mg, Ca) removal rates reach over 60%, which suggests that the QAPSU membranes have a high potential for EED application.