Abstract: Anatomically,there is no exact location of the pleurodiaphragmatic spaces.Based on an analysis of the clinical manifestations of the syndrome of invasion of pleurodiaphragmatic spaces by pathogens,the ingredients of Dayuan Decoction,and the progression of the syndrome,the authors believe that the syndrome belongs to the syndrome of damp-heat in the spleen and stomach,caused by invasion of damp-heat into the spleen and stomach,with more dampness than heat.