The Br?nsted-acidic polyether ionic liquids (ILs) with different polymerization degrees (n value) were prepared via the reaction of tetramethylguanidine and epoxy ethane, followed by successive reactions with 1,3-propane sultone and trifluoromethanesulfonic acid (TfOH). The prepared ILs were characterized by infrared spectroscopy and 1H nuclear mag-netic resonance spectroscopy, and their thermal stability was determined by thermal gravimetry. The synthesized polyether ILs coupled with TfOH were used to catalyze the alkylation reaction of isobutane and isobutene for the preparation of al-kylate gasoline. The polyether ILs could improve the substrate dissolution and promote the separation of the catalyst from the products. The ideal IL (n = 94) was determined. The optimized alkylation reaction conditions covered: a VTfOH / VIL ratio of 0.35, a reaction temperature of 40 ℃, a reaction time of 50 min, and a stirring speed of 800 r/min. The conversion of isobutene was 92.4％ and the selectivity for the C8-product was 81.6％. Under optimal conditions, the catalyst life was deter-mined and TfOH showed improved cyclic performance in the polyether ILs. After 8 operating cycles, the catalytic activity of the catalyst showed negligible decline.