Conversion of methanol to olefins (MTO) over H-ZSM-22 was carried out in the pulse and the continuous-flow reaction systems. (13)C labeling technique was used to reveal the reaction mechanism. The materials retained in the deactivated catalyst were detected by GC-MS after dissolving the catalyst framework and then extracting the organic species. The adsorption of these materials in ZSM-22 channels was computationally modeled. The results showed that the olefin methylation-cracking mechanism is the main route for the conversion of methanol over H-ZSM-22. It was suggested that the blockage of the zeolite pore openings by the coke species might be the reason of the relatively rapid deactivation of H-ZSM-22, instead of the prohibition of the formation of large transition-state intermediates involved in hydrocarbon pool mechanism. (C) 2010 Elsevier B. V. All rights reserved.