The theoretic foundation of pathogenesis and treatment of coronavirus disease 2019 (COVID-19) was explored based on Li Gao’s theory of spleen and stomach. It is thought that the COVID-19 mainly attacks the lungs, but spleen deficiency and dampness abundance is the major pathological basis for its pathogenesis. In the treatment, tonifying the middle-jiao and supplementing qi, lifting clear-yang and expelling dampness with bitter-warm ingredients are the predominant methods for patients with deficiency syndrome, and a small amount of medicinals for clearing heat and draining dampness can be used as supplementary.