Nanoscale HZSM-5 zeolite was hydrothermally treated with ammonia water at different temperatures and then loaded with La2O3 and ZnO. The parent and the modified nanoscale HZSM-5 catalysts were characterized by SEM, NH3-TPD, IR and XRF. The performance of the modified HZSM-5 catalysts for FCC gasoline upgrading was evaluated in a fixed bed reactor in the presence of hydrogen. The results indicated that the modified catalyst which was hydrothermally treated at 400 degrees C exhibited excellent aromatization activity, isomerization activity and higher ability of reducing olefin content in FCC gasoline. Under the given reaction conditions, the olefin content in FCC gasoline could be decreased from 49.6 to 8.1 vol.%. The catalytic performance of the modified nanoscale ZSM-5 catalyst hardly changed within 300 h time on stream, and the research octane number (RON) of gasoline was preserved. (c) 2006 Elsevier B.V. All rights reserved.