In the manufacturing process of ultra large scale integrated circuits (ULSI), chemical mechanical polishing (CMP) has already become a practical and main planarization technology because of its global and local planarization ability. The non-uniformity of material removal on wafer surface is one of important indicators of surface precision in wafer CMP process. In this paper, According to the σ calculation method, the calculation equation of the non-uniformity of material removal was put forward. Then, the CMP experiments on the non-uniformity of material removal were conducted under different rotational speed on a CMP machine CP-4. The WaferCheck-7200 equipment, with the theory of non-contact capacitive thickness measurement, was used to detect the thickness of each point on silicon wafer surface. After calculation, the non-uniformity of material removal on the silicon surface was obtained under different polishing speed. The test results can provide some theoretical guide for further understanding the form mechanism of the non-uniformity of material removal and the material removal mechanism in wafer CMP.