The Pt/KL catalyst modified by Tm2O3 has been characterized by the n-hexane, methylcyclopentane (MCP) and cyclohexane conversion reaction. The results show that the activity for the aromatization on Pt-Tm/KL zeolite catalysts containing thulium ranging from 0.05 to 0.2 wt.-% is higher than that on the Pt/KL catalyst, and the stability of the modified catalysts is remarkably improved. The influence of thulium on the surface property of the Pt/KL catalyst has also been studied with absorbed pyridine IR spectra and adsorption of methanol.