This study has been carried out to investigate Brain in Nei-jing. The results of this study were as follows. 1. Kidney energy becomes the marrow by warm caring function of Meong-mun(命門) and the marrow becomes brain by ascending and gathering between a hole Back-hoi(百會) and a hole pung-ji(風池) 2. Brain is a sea of the marrow that five vital organs are eraporated togather. 3. In Nei-jing(內經), there is a explanation the connectin between brain and mind, thanking by drawing in a concept of head. 4. Brain regulrates physical excercise. 5. There is a direct connection between brain and biosis. 6. Brain achieves function of sense, relating with the five sensory organs. 7. Brain controls a change of emotion. 8. Brain has immunological function.