Sulfonated poly(arylene ether ketone) (SPAEK) with pendant carboxylic acid groups was synthesized. The pendant carboxylic acid groups were functionalized by unsaturated groups in order to produce a series of cross-linked SPAEK (CSPAEK) membranes. The cross-linking was employed to limit the high degree of water uptake and improve the dimensional stability of the membrane. The proton conductivity, water uptake, methanol permeability, thermal stability, and cell performance were investigated in order to evaluate the application of the prepared CSPAEK membranes in fuel cell. The CSPAEK80-20% system, CSPAEK membrane with 80% sulfonation and 20% cross-linking degree, exhibited a comparable proton conductivity to Nation 117 but much lower low methanol permeability - about a half of that of Nation 117, suggesting that it is a promising candidate as a polymer proton exchange membrane for fuel cells. (C) 2011 Elsevier Ltd. All rights reserved.