This study systematically reviews the modern research progress of sanjiao （三焦） theory in the past 20 years， and differentiates concepts such as membrane-source， membrane-interstices， and membrane-system in the study of sanjiao essence. On the basis of its core functions of transporting original qi and regulating water metabolism， the study further expands the theoretical connotation of transporting original qi， defines the application boundary of sanjiao syndrome differentiation， and clarifies the conceptual categories of "sanjiao qi-transformation" and "qi-transforming sanjiao"， which reconciles the contradictions between sanjiao as a six fu （腑） organ and sanjiao as a regional division to a certain extent， and provides a valuable exploration for the innovative development of the theoretical system of traditional Chinese medicine.