Coughing up yellow sputum frequently indicates that the patient’s respiratory tract has some problems, for example, the trachea, bronchi or lungs have been stimulated by some factors for a long time, prompting the airway mucosa to become edematous and congested, and the cup cells and glands of the airway mucosa are continuously enlarged, thus producing a large amount of secretions. These secretions are not easily expelled from the body, and when they are invaded by some bacteria or viruses, a large amount of necrotic cell tissue is produced, which gradually accumulates in the bronchi over time and eventually leads to yellow sputum. It is not comprehensive to rely solely on the color of sputum to make a diagnosis, and patients are advised to go to the hospital in time.