<p>Porous spheres are extensively employed as carriers for the adsorption or transport of functional substances, making the exploration of particle retention within them a subject of considerable importance. The intricate dynamics of particle-laden flow around three-dimensional (3D) porous microspheres are elucidated through the coupling model of lattice Boltzmann method (LBM) and discrete element method (DEM). This investigation examines how the ratios of particle-to-pore sizes and the gradation of pore sizes influence particle retention. The numerical findings indicate that, in the absence of particle agglomeration, smaller particles tend to increase the trapped solid holdup within porous media. However, once a specific particle size threshold is surpassed, the retention process becomes selective and highly specific, with the retention efficiency closely tied to the correlation between the sizes of the pore throats and the particles. The optimal retention scenario is realized when there is a precise alignment between the particle size and the dominant size distribution of the pore throats. This provides crucial insights into the structural design of porous media, with the objective of enhancing particle retention efficiency.</p>