The theory of yin-yang and 5 elements is the core theory of TCM，which runs through every aspects of the principles，the methods，the formula and the medicines in traditional Chinese medicine.This paper extracts and purifies the contents of yin and yang and five elements in The Inner Canon of Huangdi，Yellow Emperor's Inner Canon，Classic on Medical Problems，and other classics，which guides to analyze the cause of diseases，clarify the pathogenesis，guide the diagnosis，and establish the therapies，prescription and medication.Combining the ancient and modern meaning，this paper briefly explores the content of pathological diagnosis in the system of diagnosis and treatment of Yin-yang five elements in traditional Chinese medicine.