The relative motion law of the particles in slurry, with respect to the processed surface of the silicon, during the chemical mechanical planarization (CMP) of microelectronic materials is firstly discussed. The equations depicting the scratching traces of the particles in slurry on the surface of the silicon, which depend on the rotational velocities of the silicon and the pad, are obtained. It is concluded that when the silicon and pad rotate with the same rotational velocity, the material removal rate (MMR) is proportional to the rotational velocity. As an example, the scratching traces of the particles on the processed surface of the silicon are given out in the case that the rotational velocities of the silicon and pad are the same. The results are important for the understanding of the mechanism of material removal in the CMP of microelectronic materials.