When the human body is infected with bacteria, especially after tracheal infection, the human body’s neutrophils will phagocytose fine even, but when phagocytosis reaches a certain level, the cells will rupture, and after rupture, they will become mucus of pus-like nature, and mucus and water in the trachea, as well as shed respiratory epithelial cells are mixed and discharged from the trachea, and yellow-green thick sputum will be formed. Thus, it can be seen that thick yellow-green sputum is a secretion produced after bacterial infection in the airways of the respiratory tract and lungs, and it is related to bacterial infection. If yellow-green sputum appears, it is recommended to be treated with antibiotics, and after antibiotic treatment for a period of time, the sputum then has yellow-green to white.