In the chemical mechanical polishing process, the relationship of relative motion of polishing pad and polishing head plays very important role for CMP quality. This paper established the mathematical model in order to investigate the relative motion of polishing pad and polishing head. It was found that the speed ratio of polishing pad and polishing head shows great influence on the CMP uniformity. And when the value of speed ratio of relative rotation approaches 1.23, the distribution of abrasives’ trajectories is close and uniform. Theoretically, the surface quality of workpiece is better.