The invention provides a polishing technology of a zinc oxide single crystal substrate, which can meet the requirements for the epitaxial growth of a photoelectric device. The zinc oxide single crystal substrate with the surface RMS (root mean square) roughness of less than 1nm within a surface range of 10 mu m*10 mu m can be obtained through the steps of rough grinding of a single crystal, bonding, loading on a disc, mechanical rough grinding, mechanical fine grinding, mechanical rough polishing, chemical mechanical fine polishing, cleaning and packaging. The polishing technology relates to a bonding agent, a bonding technology and a technology of unloading from the disc used in the bonding process of the zinc oxide single crystal substrate, as well as grinding fluid, polishing fluid and a grinding thickness control technology used in the grinding process and the polishing process. The obtained zinc oxide single crystal substrate can be used for the epitaxial growth of a semiconductor photoelectric device.