A polishing model of chemical mechanical polishing (CMP) is established with consideration of the effects of pattern density. This paper focuses on mechanical polishing behaviors and isolates the roles of chemical effects when patterns exist. A three-link manipulator, which is in equilibrium with the polishing motion of CMP, is adopted to study the kinematics of CMP. Time-dependent removal rate formulas are presented by considering the decrement of pattern step height. The necessary parameters, wear coefficient, and loading density coefficient are obtained by fitting to experimental data and the complete model is presented.