Molecular dynamics (MD) simulation is applied in analyzing the material removal mechanism of silicon substrate under the impact of large porous silica cluster with different pore diameters. With the increasing of the pore diameter of the porous cluster, the number of the atoms removed from the impact silicon surface will firstly increase and then decrease until the cluster is adhered to the substrate, which is due to the combinational effects of plough of the cluster, adhesion between the cluster and the substrate, and permeation of the substrate atoms through the pore of the cluster. And adhesion is the most significant one among these three effects. Meanwhile, the damage of the impact substrate will become weaker due to the decreasing of the penetration depth with the increasing of the pore diameter. In addition, it is found that the effect of an enlarged real contact area between the cluster and the substrate is more significant than that of deeper penetration of the cluster in order to enhance the material removal rate (MRR) during the impact process. These findings are instructive in optimizing the process parameters to obtain lower surface roughness and higher material removal rate during the chemical mechanical polishing process. (C) 2012 Elsevier B.V. All rights reserved.