Abstract: This paper studied the pH value of slurry,polishing pressure,rotation speed and other factors on the effect of sapphire polishing rate and surface roughness.The impact of research results showed that: with the pH（9-12）increase,polishing rate increased,surface roughness after CMP increased after the first drop;with the increase of the polishing pressure and rotation speed,polishing rate increased too after the first drop,the surface roughness was as the same.The reason was that;Hydration layer which was formed on the sapphire surface affected the polishing rate and surface roughness;Heresy number which was defined by the polishing pressure and rotation speed was influence on the process of polishing.When Hersey number reached 24,sapphire polishing rate reached maximum and surface roughness were better.