The invention discloses a mouthwash, a homemaking machine, a preparation method, and an application. The mouthwash is water containing stably dissolved ozone. According to the homemaking machine and the preparation method, oxygen in air or pure oxygen is converted into ozone gas by using an ozone generation device; the produced ozone gas is delivered into water by using an aeration device, and is converted into stably dissolved ozone in water; and residual un-dissolved ozone gas is absorbed or degraded by using a tail gas absorption or degradation device. As a result of experiments, the mouthwash provided by the invention is nonirritating and causes no chemical residue. The mouthwash can be homemade, and can be used in cleaning oral cavity, removing oral odor, relieving toothache, bleaching teeth, killing oral, gum and dental plaques, and preventing and treating caries, periodontal diseases and orally infectious diseases. When the mouthwash is applied for a long term, no significant side effect is caused.