As aerospace technology and laser technology develop rapidly, higher demand for optical system is brought forward. With a number of excellent physical properties, SiC becomes a very promising material for speculums.The mechanism of polishing on SiC mirror is studied. And the key factors affecting the SiC CCOS (computer controled optic surface) polishing, such as tools, abrasives, load, speed and slurry pH are studied, chosen and Optimized.