In this study, active catalysts of platinum supported on sulfated zirconia and HY- zeolite ( Pt/SZ-HY), and platinum supported on sulfated zirconia – mHY zeolite (Pt/SZ-mHY) were prepared using two different mesopore HY zeolite and sulfated zirconia (SZ). The synthesized catalysts were characterized by X-ray diffraction (XRD), Fourier transfer infrared spectroscopy (FTIR), BET Surface area and pore volume, Field Emission Scanning Electron Microscopy (FESEM) and (EDX). The characterisation results showed that adding sulfated zirconia to HY zeolite as a composite increased the active sites on the catalyst and increased the activity of isomerization. Isomerization experiments were studied using a different range of temperature (140-200 °C), constant pressure and LHSV of 15 bar and 1 hr-1, respectively. The results showed Pt/SZ-HY composite catalyst gives 17.95 mol% conversions for n-hexane and 27.5 mol% for n-heptane at optimum conditions of 160°C, 15 bar and LHSV of 1 hr-1. On the other hand, the composite catalyst Pt/SZ-mHY with smaller pore size achieved higher conversion to isomers, also proved that the conversion to isomer was more for n-heptane than n-hexane, which achieved 73.05 mol% conversion of n-heptane, while 57.91 % for n-hexane at the optimum operation conditions.