The new type of polystyrene with pendent perfluoroalkylsulfonylimide groups polymer (PPFSI or P-SO 2 NHSO 2 R f , where P is the polymer chain, R=CF 3 , CF 2 CF 2 CF 2 CF 3 ) was prepared by chemical modification of chlorosulfanated poly(styrene-co-divinybenzene) resins with perfluoroalkylsulfonylamides R f SO 2 NH 2. Acid strength of the PPFSI was tested by the Hammett indicator method, acid contents of the PPFSI were determined by acid–base titration and the nature of chemical modification for the PPFSI was evaluated by IR, TGA and SEM. The results indicated that the PPFSI was a strongly acidic polymer, which could be tolerant of high temperature, and an effective catalyst for direct condensation of carboxylic acids and alcohols.