In the present study, we aimed to consider the name of twelve main Meridian in order to understand the concept of the Meridian system and to applicate acupuncture theory in the clinical field properly and fundamentally. We referred to several literatures on the matter and we found out that the name of present twelve Meridian was not settled until the period of Yellow Emperor's Classic. In the time of Yellow Emperor's Classic, the two theory of Internal Organ and Meridian system were combined and added new theory of ‘WoonGi'. The general rule of combination is that the component of name of Meridian consist of 'Hand' or 'Foot' , 'three Eum and Yang' and internal organ. The internal organ coupled with the root ki or middle ki of 'three Eum and Yang' and the 'Hand' or 'Foot' depend on the location of internal organ that belongs to meridian. The name of Twelve Meridian is a kind of system formed to analyze the two concepts organically and dynamically. One is material internal organ and the other is immaterial meridian system.