A novel kind of zwitterionic polymer, tertiary amine-modified PES (TA-PES), bearing cationic tertiary amine groups and anionic sulfonic groups, was synthesized in this study. The as-synthesized TA-PES was employed to fabricate ultrafiltration membranes by phase inversion in a wet process using pure water or sodium chloride aqueous solution as coagulation bath. It was found that the as-fabricated ultrafiltration membranes exhibited distinct ion-strength-dependent flux due to the inherent zwitterionic characteristics of TA-PES. The permeation flux of TA-PES membranes can be varied dramatically by simply changing the ionic content in coagulation bath. Furthermore, TA-PES membranes displayed superior anti-protein-fouling property and desirable ultrafiltration performance. (c) 2008 Elsevier B.V. All rights reserved.