Novel sulfonated poly(arylene ether ketone)s were prepared directly by aromatic nucleophilic polycondensation of 4,4'-sulfonyldiphenol with various ratios of 4,4'difluorobenzophenone to 5,5'-carbonylbis(2-fluorobenzenesulfonate) in dimethyl sulfoxide. The resulting polyelectrolytes were characterized by IR, NMR, TGA and DSC. The 10% weight loss temperature of the products is higher than 510degreesC, and their glass transition temperature is above 260degreesC. The introduction of 4,4'-sulfonyldiphenol with powerful electron-withdrawing group, -SO2-, into the main chain of sulfonated poly(arylene ether ketone)s improves the thermal stability against desulfonation. The ion-exchange capacity and swelling of the polyelectrolyte membranes were measured, which are higher than 1.23meq/g and not higher than 20.9%, respectively. The membranes show very good perspectives in polymer electrolyte fuel cell (PEMFC) application.