Abstract：Pulmonary nodules have garnered significant attention in contemporary clinical practice. Guided by the theory that "most diseases are caused by phlegm，" this paper employs "phlegm" as its central argument to explore the etiology， pathogenesis， and syndrome characteristics of pulmonary nodules. It elucidates the pathology of pulmonary nodules by analyzing the nature of "phlegm" and its role as a pathogenic factor in their development. Finally，the paper addresses diagnostic and treatment approaches for pulmonary nodules from the perspective of "phlegm" causing "accumulation".