Abstract: Using sodium hypochlorite as oxidizer, calgon as complexing agent, OP-10 emulsifier as surface active agent and silica sol as abrasive to make up slurry (pH 9), chemical mechanical polishing of large diameter thickness ratio copper sheet after coarse polishing was carried out. The surface roughness and the flatness of the copper sheet before and after polishing were measured. The elements on the surface of the copper sheet were analyzed by X-ray spectrometer, and the surface phase and residual stress of the copper sheet were analyzed by the X-ray diffractometer. Results show that the flatness PV of the copper sheet is reduced from 4.813 μm before polishing to 2.917 μm after polishing, and the surface roughness R_a decreases from 31.373 nm to 3.776 nm. There is no obvious change in the elemental composition and the phase of the surface of the copper sheet before and after polishing, and the chemical and mechanical effects have reached the balance. The mechanical action of the abrasive and the polishing pad can quickly remove the oxide layer on the surface of the copper sheet. The chemical mechanical polishing can significantly reduce the residual stress on the surface of copper after rough polishing.