The respiratory device is useful for improving the ventilation of the respiratory tract, but only as a temporary, complementary correction of the habit of breathing through the mouth in children, or in other special populations of adults. The main purpose is to improve the habit of mouth breathing by training the muscles of the two lips, so that the person can breathe through the nose as much as possible. Clinically, it is not possible to use the respiratory device for a long period of time, otherwise it is likely to become dependent, creating physical and psychological dependence, which may degrade the function of nose breathing in the long run. During the correction process, the nose is used constantly for active breathing, and the mouth is not used to breathe as much as possible to form a virtuous cycle, gradually removing the respiratory device to form an independent, active nasal breathing.