Diamond is an important material for future technology due to its unique properties, but poor surface quality can affect its application in high-tech fields. Therefore, it is the key for diamond applications to achieve diamond ultra-precision machining. Chemical mechanical polishing (CMP) is an important process for achieve global planarization in integrated circuits, enabling diamond ultra-precision machining. The existing processing methods and CMP research status of diamond are introduced as well as the advantages and disadvantages of other processing methods (mechanical polishing, tribo-chemical polishing, thermo-chemical polishing, etc.) are compared. Other processing methods have problems, such as serious damage to the surface after processing and incomplete processing surface roughness. The CMP of diamond has undergone a development process from high-temperature polishing to room-temperature polishing. The process equipment is simple, low in cost, and the surface roughness after polishing can reach sub-nanometer level. In addition, the molecular dynamics (MD) simulation of diamond make us have an insightful understanding on the interaction of nanoparticles and polishing mechanism during diamond polishing process from atomic perspective. Although there are still many problems to be solved in diamond CMP process, its development prospects are still very optimistic.