The growth of epitaxial layer of SiC wafer requires the surface of SiC substrate to reach an atomic scale accuracy.To solve the problems of low machining efficiency and low surface accuracy in the polishing process of SiC wafer, a novelultra-precision machining method based on the synergistic effect of chemical reaction and flexible mechanical removal ofthe magnetorheological (MR) effect, the MR-chemical mechanical polishing (MRCMP) is proposed. In this technique,magnetic particles, abrasives and chemical additives are used as MR-chemical polishing fluid to form a cluster MR-effectflexible polishing platen under an applied magnetic field, and it is expected to realize an atomic scale ultra-smooth surfaceplanarization with good controllability and high material removal rate by using the flexible polishing platen. Polishingexperimental results of C surface of 6H-SiC crystal substrate indicate that an atomic scale zero-defect surface can beobtained. The surface roughness of C surface of SiC wafer decreased from 50.86nm to 0.42nm and the material removal ratewas 98nm/min when SiC wafer was polished for 60 minutes.