Abstract：Phlegm rheum is the essential manifestation of airway mucus hypersecretion. The lung governs regulation of the waterways， and is directly involved in the formation of phlegm rheum. The spleen governs transportation and transformation，ascent of the clear and the muscles；it associates with thought in emotions，and a vigorous spleen allows the body to resist pathogens throughout the four seasons. These characteristics of spleen can affect the generation and distribution of phlegm rheum. This paper discusses the internal mechanism of airway mucus hypersecretion from the theory of lung and spleen，and guides the clinical prescriptions and medication，which may have an important enlightening effect.