Abstract: The reaction mechanism of hydroisomerization of n-alkanes, from n-decane to n-tetrodecane, over Pt/SAPO-11 catalyst was studied. Results indicated that the n-alkanes with different carbon atom numbers exhibited higher isomerization selectivity at lower temperatures. The isomerization selectivity of n-alkanes can reach 90% by controlling temperature to keep the conversion rate lower than 85%. The conversion rate of n-alkanes was increased and the selectivity of isomerization was decreased with the increase of carbon atom number and temperature due to the occurrence of cracking reaction. Bifunctional catalyst has a good product shape selective effects. The isomerization products are mainly composed of unilateral chain isomers which have the methyl at the end and the center of the carbon chain. At low conversion rate, the cracking reaction of the long-chain n-alkanes over the Pt/SAPO-11 catalyst was mainly catalytic hydrocracking, the carbon number distribution of the cracking products was uniform. However, at high conversion rate, the reaction was mainly acid catalytic cracking, the carbon number distribution of cracking products was obvious asymmetric distribution.