This modeling study investigates the influence of spatially distributed pore size and porosity on diffusional and reactive features inside the methanol-to-olefin (MTO) porous catalyst particle. The model developed in this study integrates mass, momentum and heat balance equations, spatial pore size and porosity distribution models, multicomponent diffusion and lumped kinetic models. The proposed model was first validated by using the experimental and empirical data. The simulation results demonstrated that the pore diameter and porosity that decrease toward the particle core is the optimal distribution for the MTO catalyst particle. Subsequent parametric sensitivity analysis indicated that the temperature plays the most significant role in the effectiveness factor. The smaller pore diameter favors the larger ratio of the ethylene to the propylene. Comparing with the traditional trial-and error methods, the proposed model is simple but effective, which is valuable for the design and optimization of porous catalyst particles. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.