Abstract: Though intelligent Agent can be considered as an entity from outside, it shows the property of separation because of its need inside. The conclusion is put forward based upon the thought that EGO is used to indicate the center of intelligent Agent's spirit. The multiple characteristics of Agent's need and desire are revealed in this paper, and the qualities and characteristics of Agent's separation are analyzed and discussed further. The knowledge about Agent's structure lays a foundation to analyze its behavior according to its structure.