In this study, orange peel oil which had been produced by cold press technique was processed. The catalytic reaction of limonene composed of 90–95% of the orange peel oil carried out in different supercritical alcohols, and it was obtained the compound p-cymene mainly. The experiments processed in a packed bed reactor using Pt/Al2O3, Ni/Al2O3 and Pd/Al2O3 catalysts in over supercritical conditions of ethanol and 2-propanol. Experiments of reaction time, temperature and pressure scanning were carried out in the ranges of 10–50s, 245–340°C and 6.5–12.5MPa, respectively. It was observed that Ni/Al2O3 was ineffective to the conversion of limonene. However, when Pd/Al2O3 and Pt/Al2O3 catalysts were used, p-cymene was produced mainly. Especially, when Pd/Al2O3 catalyst was used, it was detected that limonene converted completely and obtained p-cymene in yield of 80%. Furthermore, p-cymene selectivity of Pd/Al2O3 was much better compared with Pt/Al2O3.