Novel sulfonated poly(phthalazinone ether ketone)s were synthesized directly by aromatic nucleophilic polycondensation of 4-(4-hydroxyphenyl)pthalazinone with various ratios of 5,5'-carbonyl-bis(2-fluorobenzenesulfonate) to 4,4'-difluorobenzophenone. The 10% weight loss temperature of the products is higher than 500degreesC. The resulting ionomers show low swelling (14.7, 16.7 and 17.8%), while the corresponding IEC are 1.58, 1.88 and 2.16 meq/g, respectively. The low swelling results from hydrogen bonding. The membrane show very good perspectives in polymer electrolyte membrane fuel cell applications.