Chronic bronchitis （CB） is a common respiratory system disease that is classified as a lung disease in traditional Chinese medicine （TCM） and is closely related to lung dysfunction. Lung Yang is the Yang Qi of the lungs，which drives the physiological activities within the lungs. It has physiological functions such as warming the lung system，regulating lung fluid，and dispersing the protective Yang. It can be distributed on the surface of the airway's Yin skin through sweat pores in the form of airflow and fluid，playing a protective and nourishing role. If the protective Yang fails to guard the Yin skin or if the lung fluid cannot nourish the Yin skin，the structural integrity of the airway's Yin skin may be compromised. This may weaken lung Yang's functions， such as clearing phlegm turbidity，dispersing lung fluid，and resisting external pathogens. Consequently， the retention of phlegm turbidity，insufficient nourishment of the Yin skin，and invasion by external pathogens all damage the lung Yang，burn the lung fluid，and exacerbate the pathological state of Yin skin unprotected，forming a vicious cycle that ultimately results in lung Yang asthenia and then the onset of CB. Based on the intrinsic connection between "Yin skin unprotected" and "lung Yang asthenia"，this paper interprets the etiology and pathogenesis of CB. It proposes that "Yin skin unprotected" in the airway is the basic cause of CB and "lung Yang asthenia" caused by "Yin skin unprotected" is the core pathogenesis of CB. By integrating micro differentiation indicators with macro differentiation syndromes， the study explores its modern biological basis. Guided by the theory of "warming the lung Yang and protecting the Yin skin" and based on modern pharmacology research，this study further explores the scientific connotation of single TCM and compound formulations for treating TCM by warming the lung Yang and protecting the Yin skin. Furthermore， it proposes methods for dispelling pathogenic factors and protecting the Yin skin during the acute exacerbation phase，as well as nourishing and warming lung Yang during the remission phase，in order to provide new ideas for the early prevention and treatment of TCM.