Processing is the main characteristic of the products used in traditional Chinese medicine (TCM), and this is how they differ from natural medicines. The characteristics of the medicines used in TCM have rich scientific connotations. Because of the complexity and diversity of TCM, the processing mechanism has not been fully elucidated. In recent years, the theory of component structure has been put forward and applied to guide TCM research, resulting in substantial progress. This paper presents a systematic review of mechanism research in TCM processing. It can be used as a reference of the ideas and methods of component structure theory for studying component content changes caused by processing, for studying in vivo changes in components caused by processing, for studying the effects and toxicity changes in components caused by processing, for studying metabolic changes of components caused by processing, and for developing component structure theory in the study of the mechanism of TCM processing. Combining component structure theory with various new methods and technologies will enable better understanding of the processing mechanisms of TCM and speed up the modernization of TCM.