The principles of medicinal classification and application in Zhang Congzheng's pathogen-expelling system were derived from his extensive clinical experience， reference to the classification of medicinal properties， and a deep understanding of the efficacy and trends of medicinal actions. These principles are crucial for linking the pathogen-expelling theory to specific formulas and are indispensable. By returning to the historical context in which Zhang Congzheng lived， this paper clarifies the relationship between the three pathogen-expelling methods and the medicinal classification. It also attempts to interpret the connection between the sweating method and Fuling （Poria）， as well as the connection between emetic and purgative methods and Guati powder. The paper aims to provide theoretical support for the inheritance of Zhang Congzheng's pathogen-expelling system， and to offer new perspectives and insights into the understanding and application of pathogen-expelling medicines.