Objective]To explore the essence of doubts differentiation from‘Neiwaishangbianhuolun’,the monumental work of the medical practitioner Dongyuan Li in Jin and Yuan Dynasties, and relativity between internal damage and exogenous diseases.[Methods] By means of researching the background of‘Neiwaishangbianhuolun’, analyzing the 13 main differentiations, think about the essence of doubts differentiation; meanwhile, by connecting to the explicate of mechanism of ascending yangqi belonging to exterior-releasing medicine(wind-expel ing drugs) in his representative work‘Piweilun’, discuss the contrary and transforming relationships between exogenous wind-cold and internal damage of the stomach and spleen, comparing to academic thoughts of Zhongjing Zhang’s‘Shanghanlun’. [Results]Realize essence of doubts differentiation from ‘Neiwaishangbianhuolun’ is not exterior or interior of disease location,but deficiency and excess of disease character.By analyzing the functional mechanism of wind-expel ing drugs and relationship among exogenous diseases,wind-expel ing drugs and the stomach and spleen, raise the relativity between internal damage and exogenous diseases. [Conclusions] The revealing of the essence of deficiency and excess differentiations from‘Neiwaishangbianhuolun’, together with knowledge of the functional essence of wind-expel ing drugs and the relevance of internal damage and exogenous diseases, may open the mind partly for syndrome differentiation and medications in the clinic.