Corona virus disease-2019(COVID-19) belongs to the category of plague of traditional Chinese medicine. Based on the epidemic situation of COVID-19, we have summarized the classical Chinese medicine theories in guiding the understanding, prevention or treatment of COVID-19 by searching the understanding and application of doctors. The theories include: the theory of “preventive treatment of disease” focused on “improving the prognosis of the disease”, the theory of “the three categories of etiological factors” based on “dynamic and holistic view”, the theory of “febrile diseases due to latent Qi” valued asymptomatic cases, the theory of “Treatise on Warm Pestilence” supposed to put dispelling pathogenic factors in the first place, the theory of “Treatise on differentiation and treatment of epidemic febrile disease” treating damp-warm disease by three-Jiao syndrome differentiation, the theory of “Treatise on Cold Damage Diseases” emphasized to grasp the pathogenesis of diseases and treat it with the evidences and the theory of “Clarifying Doubts about Damage from Internal and External Causes” proposed the disease is caused by the insufficiency of Zhong qi.