A method of supplying oxygenated water is performed on a water tank, in which oxygenated water is received. The method lets the water tank supply a constant amount of the oxygenated water once, and then supply the water tank with water and pure oxygen to recover the dissolution ratio of oxygen of the oxygenated water in the water tank. The method may supply a constant amount of oxygenated water every time for the user to drink it up once.
