Zeolite NaY and Naβ were modified by cation exchange and hydrothermal treatment to make a series of modified catalysts, including HY, USY, CeY, MgY, Hβ and USβ. The catalytic activities of the modified catalysts for the alkylation of thiophenic derivative with olefins in FCC gasoline were investigated. The surface acidity of modified zeolite had been studied by FT-IR. The results show that Y zeolite exchanged by ammonium have much more acid than β zeolite. The volume of B acid and L acid of USY increased to 868.583 μmol/g and 972.869 μmol/g , while L acid is mainly in the form of weak acid. The volumes of B acid and L acid of USβ also increase with the decreasing of strong B acid and increasing of strong L acid. The volume of total acid of MgY is slightly lower than HY, but with only 86.742 μmol/g strong B acid and only 31.335 μmol/g strong L acid. The volumes of total B acid and strong B acid of CeY are slightly lower than USY, with only 58.308 μmol/g total L acid and non of strong L acid. Through the analysis of surface acidity of zeolite and alkylation activity, it shows that the more total B acid and strong B acid (except HY), the higher conversion of sulfur compounds below 100 ℃ fraction of FCC gasoline. Strong L acid is not conducive to the alkylation. The strong B acid is the main active site of alkylation.