To explore the theoretical basis of nourishing yin and resolving phlegm method and the characteristics of stage drug use.Inquire literature and seek the internal relationship between phlegm,dampness,water,drink and body fluid,blood and yin essence,and to expound the theoretical basis and characteristics of nourishing yin and resolving phlegm method.We put forward that expectorant is the key to the diagnosis and treatment of corona virus disease 2019(COVID-19)in traditional Chinese medicine.Phlegm,drinking,dampness,body fluid,blood,and yin essence belong to the category of yin.Clinical syndrome can be evaluated based on the degree of yin injury and phlegm dampness.