Abstract: The aromatization and olefin-reduction catalyst M had been applied in commercial unit for desulfurization and olefin-reduction process of FCCG heavy fraction. To overcome the shortcomings of lower liquid yield and shorter cycle length at higher reaction temperature, a series of modification procedures were taken to improve the activity and stability of the catalyst M. A modified catalyst M-II was then successfully developed by improving manufacture of HZSM-5 and the ratio of the active metals. The results of the performance test of M-II, compared with that of catalyst M, show that aromatics increases more than 1.3 % and RON is 0.7 higher than M at the close reduction level of olefin.