Bronsted-Lewis acidic ionic liquids [3-(1-Py)-(CH2)3-SO3H]Cl-xSnCl2 wi-th different mole fractions of SnCl2 was prepared(where x is the mole fractio-ns of the Lewis acid).The acidity of the group was characterized and compare-d to each other by means of FTIR in virtue of pyridine molecular probe,the d-ual acidic ionic liquids were then employed to the synthesis reaction of di(2-(2-butoxyethoxy)ethanol) terephthalate.The influences of catalyst type and amount,ratio of reactants,dosage of water-entrainer,reaction temperature,reaction time we-re investigated .In addition,the target product by 1HNMR .The results show that [3-(1-Py)-(CH2)3-SO3H]Cl-0.5SnCl2 had the highest catalytic activity.With [3-(1-Py)-(CH2)3-SO3H]Cl-0.5SnCl2 as catalyst,the optimal reaction conditions were as follows:n(DGBE):n(PTA)=2.3:1,catalyst (4.0% of mass of PTA),water-entrainer (60.0% of mass of PTA),reaction time (2.5h) and the speed stirring was 300r/min.the esterification rate was 99.43%.Catalyst in the case of without any proc-essing, can be recycled five times.