Transformation of n-octene has been investigated over nanoscale HZSM-5 at different reaction temperature and contact time. The results show that the main reaction was isomerization of n-octene over 200 C. Hydrogen transfer reaction also occurred at 200 C, but the products were alkanes and cycloolefins instead of aromatics. The aromatization was promoted by high temperature. The maximum selectivity of i-paraffins occurred between 300 and 350 C. Propene, butene and pentene were the primary cracking products. These olefins were oligomerized and cracked to produce a wide distribution of olefins with different carbon atoms. These intermediates then were quickly transformed into aromatics and alkanes by hydrogen transfer over acid sites at high reaction temperature. Propane and butane can be transformed into methane and ethane at long contact time above 400 C.