High quality sapphire material has a series of characteristics, such as high strength, high hardness, high temperature resistance, abrasion resistance, strong corrosion resistance, excellent light transmittance and electrical insulation. Therefore, as an important technical crystal material, sapphire wafer has been widely used in a series of high-tech fields, such as laser window and mirror, epitaxial substrate of semiconductor silicon, integrated chip of insulating substrate, industrial infrared light transmitting material, epitaxial substrate material of semiconductor gallium nitride, etc. it has also been widely used in civil industry. Sapphire chip is still an economical, mature and large amount substrate material of gallium nitride.