In this paper, the mechanism of chemical mechanical polishing ( CMP ) was summarized. The development of chemical mechanical polishing of three kinds of substrates ( α-Al₂O₃, SiC, Si) were introduced. The study was mainly focused on the effects of the polishing process parameters and the composition of the polishing slurry ( different abrasive, abrasive particle size, oxidizing agent, chelating agent and pH value, etc) on wafer polishing, and the existing problems of CMP were pointed out. Finally,the future prospect of CMP of LED substrate was outlined.