Objectives : The purpose of this study was to inquire clinical meaning and characteristic of Eight extra meridians(奇經八脈) by researching building and progression of Eight extra meridians theory. Results : As a result of research of building and progression of Eight extra meridians(奇經八脈) theory, we can regard that the origin of Eight extra meridians was based on lower Danjeon(丹田) which was the root of Primordial energy and the origin of the Twelve meridians and collaterals(十二經脈) was based on Middle energizer which was the root of Acquired energy. On this, we could know that Eight extra meridians and the Twelve meridians and collaterals are based on Primordial energy and Acquired energy and function of Eight extra meridians and the Twelve meridians and collaterals are complement each other. So, we can say that considering the Twelve meridians and collaterals means that is valued on Acquired energy clinically, and considering Eight extra meridians means that is valued on Primordial energy in health preserving method (養生).