The main purpose of lip retraction breathing training is to improve lung function, which is an adjunctive therapy of respiratory training mainly for respiratory diseases that cause lung function to decline, such as chronic obstructive pulmonary emphysema and pulmonary heart disease that occur when the residual air volume in the lungs increases and the elastic retraction force of the alveoli decreases. The lip retraction breathing training allows the respiratory muscles to be contracted and relaxed to a certain degree, which can enhance the improvement of the respiratory movement of the diaphragm. In addition, the residual gas in the lungs can be expelled as much as possible in this way, so that the gas in the lungs can be expelled more easily and the symptoms of hypoxemia and even hypercapnia can be alleviated.