Objective : The concept of Eum-Fire(陰火), which was brought up by Li Dong-yuan(李東垣), is such a very ambiguous thing that many medical scholars had tried to understand its real meaning. Trying to understand the real concept of Eum-Fire, this study goes on based on the view that the concept of Eum-Fire in the medical books of Li Dong-yuan was used as being the same thing with the concept of Xim-Fire(心火) and Premier-Fire(相火), and the substance of this kind of fire is the fire in Ximpo(心包) and Myungmun(命門) which works in the system of Ximgye(心系). To verify this view is the main objective of this study. Method : Inquiring into Li Dong-yuan's medical books, this study investigated examples of the uses of the terms of Eum-Fire, Xim-Fire and Premier-Fire, and analyzed the relation between the meanings of these terms. And as a ollateral evidence to the main view of this study, this study notes Wang An-dao(王安道)'s reference about Eum-Fire and inquires into the concept of Premier-Fire that was formed by Liu He-jian(劉河間), who had been referred to in Wang An-dao's argument about Eum-Fire. And this study also presents the Chen Shi-duo(陳士鐸)'s view about Eum-Fire that is expected to show a more concrete concept of Eum-Fire than now and seems to deserve to be compared with that of Li Dong-yuan. Result and Conclusion : It could be understood that the concept of Eum-Fire in Li Dong-yuan's books was used as a thing that owns the same substance as a kind of fire with Xim-Fire and Premier-Fire. In this viewpoint it could also be understood that Li Dong-yuan had attached the concepts like Xim-Fire and Eum-Fire to the concept of Premier-Fire, so terms like these could be understood as such concepts that represented the diverse figures of Premier-Fire. And this study also found that the substance of Xim-Fire as a kind of Premier-Fire means the fire of Ximpo and Myungmun that works in the system of Ximgye, which seems to be formerly introduced as a frame of Premier-Fire by Liu He-jian. This study also found the indirect basis of this viewpoint in the books of Chen Shi-duo, and could get a conclusion that Chen Shi-duo's view about Eum-Fire can be regarded as a thing that could show us more concrete matter of Eum-Fire than now.