Abstract： Objective： To explore the theory of pathogens lurking in the membrane source and review the correlation between Dayuan Decoction and this theory in modern literature， as well as the principles， methods， formulas， and herbs in the application of Dayuan Decoction for treating epidemic diseases. Methods： Using China National Knowledge Infrastructure （CNKI） as the literature retrieval platform，articles on the prevention and treatment of epidemic diseases with Dayuan Decoction from January 1， 1984， to December 31， 2023， were retrieved. A database was established to categorize and analyze the literature volume， clinical symptoms， tongue and pulse manifestations， and pathogenic factors related to the use of Dayuan Decoction in epidemic diseases prevention and treatment. Results： Dayuan Decoction is mainly used for fever， COVID-19 infection， and severe acute respiratory syndrome （SARS）， and other diseases. The application of Dayuan Decoction for treating epidemic diseases peaked during outbreaks. Its typical clinical manifestations include high fever or alternating chills and fever，dry mouth without desire to drink， chest and epigastric stuffiness and distension， wiry and slippery pulse， and yellow greasy tongue coating，which are highly consistent with the clinical presentations of both damp-heat epidemic pathogens lurking in the membrane source and damp pathogens lurking in the membrane source. Conclusion：The theory of pathogens lurking in the membrane source plays a key guiding role in the syndrome differentiation and treatment of epidemic diseases with Dayuan Decoction.