Intraparticle　diffusion　inside　porous　pellets　plays　a　controlling　step　in　most　reactive　transport　processes.　In　order　to　investigate　microscopic　diffusion　process　in　porous　pellets　with　macro-mesopore　structure,　a　three-dimensional　lattice　Boltzmann　method　(LBM)　approach　with　multi-relaxation-time　(MRT)　collision　operator　was　utilized　to　calculate　the　intraparticle　diffusivity.　With　respect　to　the　hierarchical　pore　structure,　the　modified　random　generation　of　macro-meso　pores　(RGMMP)　algorithm　was　proposed　to　obtain　pore　structure　of　porous　pellets.　In　this　work,　a　resin　catalyst　that　has　macro-mesopore　structure　was　selected　as　a　validation　example.　Based　on　the　LBM　approach,　the　effects　of　four　geometrical　parameters　of　the　modified　RGMMP　algorithm　on　the　intraparticle　diffusivity,　namely　the　total　porosity,　the　ratio　of　mesopore　porosity　to　macropore　porosity,　the　ratio　of　average　macropore　diameter　to　mesopore　diameter　and　the　macropore　growth　direction　were　investigated,　so　as　to　elucidate　the　mass　transfer　mechanism　in　porous　pellets　with　macro-mesopore　structure.　These　theoretical　findings　are　useful　for　the　pore　structure　optimization　design　of　porous　pellets　with　macro-mesopore　structure.　(C)　2019　Elsevier　Ltd.　All　rights　reserved.