A series of novel ionic cross-linked sulfonated poly(ether sulfone) (SPES)-based proton exchange membranes (PEMs) were successfully constructed by using quaternized graphene oxide (QGO) as the inorganic fillers and cross-linking agents. The ionic cross-linking networks were implemented by the interactions between the sulfonic add groups of SPES and the quaternary ammonium groups of QGO. The influences of different loading contents of QGO on the properties of the ionic cross-linked composite membranes were studied. The composite membranes showed the enhanced mechanical properties and improved oxidative stabilities. Meanwhile, the swelling ratio, water uptake and methanol permeability of the ionic cross-linked SPES/QGO composite membranes were much lower than that of the pristine SPES membrane. The swelling ratio and water uptake of SPES-10-QGO composite membrane had the minimum values among all the composite membranes. In addition, although the proton conductivity of ionic cross-linked SPES membranes by QGO decreased, SPES-10-QGO still exhibited high proton conductivity of about 0.08 S cm(-1) at 80 degrees C. All the results indicated that the ionic cross-linked composite membranes with balanced properties were the potential candidate materials for PEMs. (C) 2016 Published by Elsevier B.V.