In this work, a Random Needles Model is employed to investigate the effects of the hierarchical pore structures and geometries for the extruded hydrodemetallization (HDM) catalyst pellets of the rodlike catalysts on the reaction-diffusion behaviors at the pellet scale. Under the fixed total porosity, increasing the mesoporosity of the pellet with a given spherical geometry leads to the shift of the HDM process from the reaction-controlled regime to the diffusion-controlled one. The contributions of the macropore and mesopore diameters to the total reaction rate are disentangled. Further understanding of other given geometries shows a linear correlation of the reciprocal pellet's characteristic size with the initial internal effectiveness factor and the highest HDM reaction rate for the trilobular pellet. Finally, the height of the trilobular pellet is optimized under the given geometric volume.