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 .