Abstract: Experiments for coke deposition and deactivation of Pt/HZSM-5 reforming catalyst were carried out on a continuous fixed-bed micro-reactor by using n-octane as model compound. TG-DSC, N2 adsorption, XRD, NH3-TPD，FT-IR and TEM were used to characterize the fresh and deactivated catalyst samples for studying the effect of coke deposition on the physical properties of catalyst. Results showed that the coke deposits on the deactivated catalysts were mainly nano-tubular type and most of them were in the less than 4 nm microspores, which caused the reduction of specific surface area and pore volume, as well as the increase of average pore diameter. In addition, the crystal structure of coked ZSM-5 zeolite changed from monoclinic to orthorhombic system. The coking reactions preferred to happen on the strong acid sites, with the increase of coke deposits, the number of Bronsted acid sites and Lewis acid sites decreased significantly, in which the reduction of the former was more obvious.