As aerospace technology develops rapidly, higher demand for aerospace optic system is brought forward. With its excellent physical qualities, SiC becomes a very promising material for speculums. The material-remove mechanism of SiC surface polishing is studied, that is, the grinding mechanism of ceramic material. Indentation fracture model is also introduced and is used to explain material-remove mechanism of SiC surface polishing, and the model of SiC polishing in ideal condition is analyzed. Finally, the material-remove mechanism of SiC polishing in real state is studied.