The invention provides a method for preparing a high-quality wafer-level graphene single crystal, comprising: placing the plasma-treated metal foil in a reaction furnace and passing it into an inert atmosphere, then raising the temperature to the annealing temperature and then passing hydrogen gas Carry out annealing treatment, the metal foil is a kind of in copper foil, nickel foil, molybdenum foil, cobalt foil; Into the reaction furnace, introduce carbon source, adjust the annealing temperature to the growth temperature of graphene single crystal and then start graphene single crystal After the growth is completed, cool to room temperature; the atmosphere of the plasma treatment is at least one of air, hydrogen, argon, oxygen and nitrogen, the power is 100-150W, the pressure is 400-500Pa, and the time is 1 ~30 minutes.