Magnesium oxide (MgO) is an excellent single crystal substrate and is widely used in the production of ferroelectric thin films, magnetic thin films, optoelectronic thin films and high-temperature superconducting thin films. Since its dielectric constant and loss in the microwave band are very small and it can obtain large-area substrates (diameter 2 inches and larger), it is one of the important high-temperature superconducting thin film single crystal substrates for current industrialization. It can be used to make high-temperature superconducting microwave filters and other devices required for mobile communication equipment. Profit can provide high-purity, low-cost MgO single crystals with a size of about 2”x2”x1”, and use chemical mechanical polishing to prepare high-quality atomic-level surface substrates.