Understanding the flow behaviors and pressure distribution in the interstitial void space among particles is of great importance for improving operating parameters of fixed bed chemical processes, like OCC (olefin catalytic cracking) process. Particle-resolved simulation method is extensively adopted in simulations of fixed bed reactors due to its ability of accurate describing fluid dynamics in packing structures, but its mesh generation process is rather difficult when the packing structure is complex. This study realized a particle-resolved simulation method of typical packing structures in the OCC fixed bed reactor through developing an immersed boundary method, which was based on the porous media model (PMM-IBM) and mesh adaption technology. This method simplified mesh generation process and reduces the computational cost. Compared to the uniform mesh, the total mesh number of the packing structure was reduced about 80% after the mesh adaption. The key parameters of the PMM-IBM were first determined by comparing the forces acting on the particle surface between PMM-IBM and body-fitted mesh method. Further, for three different bed-to-particle diameter ratios, the voidage, pressure and velocity distribution of the packing structures were simulated. It was found that the maximum local axial velocity in the packing structures was 10 times higher than the inlet velocity. The radial distribution of the average axial velocity was consistent with that of the average axial voidage, which showed an oscillation attenuation trend along the center of the bed. Moreover, the pressure drop was almost consistent with the results from Reichelt empirical correlation. Finally, the mass transfer and the main reaction of OCC were considered. The mass fraction variation of the reactant according to pore size and porosity was predicted, which provided the possibility for including the external flow structures and variations in future work.