Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on NaY-and HY-zeolite were examined as a catalyst for producing gasoline from n-decane via simultaneous reforming and cracking. The catalysts were prepared by calcining and reducing metal-ion-exchanged Y-zeolite with O₂ and H₂ at 300℃, respectively. Thus prepared catalysts were characterized by hydrogen chemisorption and temperature programmed desorption of ammonia. Pt-Ni/NaY and Pt-Ir/NaY bimetallic catalysts offered the improved activity maintenance compared to Pt/Nay monometallic catalyst. The catalysts supported on HY-zeolite showed higher selectivity toward C₅-C₇ and C₈-C₁₀ than those of the catalysts supported on NaY-zeolite, which is a desired characteristic for increasing octane value of gasoline these days. However, deactivation with reaction time was much more pronounced on HY-zeolit-supported catalyst. When the catalyst was presulfided with H₂S, the stability with time on stream was enhanced and the selectivity was quite different from that of the catalyst before presulfiding. The acidity of Y-zeolite and presulfiding of catalyst greatly influenced the activity, selectivity and stability of Pt, Ir, Pt-Ir and Pt-Ir and Pt-Ir and bimetallic catalysts supported on Y-zeolite in n-decane reforming reaction.