A kinetic model for methanol to olefins (MTO) process over SAPO-34 catalyst was established based on the dual-cycle reaction mechanism. Simplifications were made by assuming olefins-based cycle as virtual species S, and aromatics-based cycle as R, where the former mainly accounts for the production of higher olefins, while the latter for lower olefins. Transformation of S to R was considered with the participation of methanol and olefins. Meanwhile, a phenomenological deactivation model was developed to account for the deactivation process. With the proposed model, the evolution of methanol conversion and product selectivity with time on stream could be predicted, and key reaction characteristics, such as the autocatalytic nature of the reaction, could also be captured due to its mechanism-based nature. Further simulations of MTO reactors at different scales validated the robustness and applicability of the current model in MTO process development and optimization. (c) 2018 American Institute of Chemical Engineers AIChE J, 65: 662-674, 2019