A series of crosslinkable sulfonated poly(ether ketone)s containing cycloalkenyl groups were synthesized by aromatic nucleophilic substitution reaction. To decrease the swelling of fuel cell membranes, crosslinking of theses polymers by radical polymerization has been explored. These polymeric films exhibit good thermal and oxidative stability, and good dimensional stability in hot water. The proton conductivity of one example at room temperature is 7.52*10−2 S/cm. The results showed that these materials containing cycloalkenyl groups are possible inexpensive candidate materials for proton exchange membranes in fuel cell applications.