HY zeolite modified by La2O3 on olefin alkylation of thiophenic sulfur in fluid catalytic cracking (FCC) gasoline was studied in the micro fixed-bed reactor. Reaction pressure 1.5 MPa, reaction temperature 180 A degrees C, WHSV 3.5 h(-1), using HY zeolite modified by 2% La2O3, the conversion of thiophene sulfur promoted nearly 10% with good selectivity, comparing with no-modified by La2O3. Acidity of modification of HY zeolite with La2O3 was tested in Pyridine-IR, it showed that increasing the amount of weak Bronsted (B) acid and the ratio of total B acid with total Lewis (L) acid could strengthen the hydrogen transfer activity of the catalyst, which leaded to improving the capacity of thiophene alkylation. The X-ray diffraction (XRD) results showed that the structure of catalysts could be optimized by loaded proper amount of La2O3 for promoting the acidic properties of HY zeolite.