Abstract: Benzene alkylation process is a typical catalytic reaction. When the reaction is carried out in gas phase or liquid phase, obvious catalyst deactivation is observed. This paper aims at slowing down catalyst deactivation of benzene alkylation reaction by taking advantage of some special properties of supercritical fluids (higher solubility than gases and higher diffusibility than liquids). The results indicate that when the reaction condition is above the critical point of the mixed reactants, the coke precursors (polynuclear aromatics) which directly deactivate catalyst can be removed by dissolution in the supercritical fluids, which leads to a longer catalyst life.