Recently South Korea, China, and Japan have established or expanded their responding ADIZ without the basis of any international law to implement each government’s maritime policy and to project their air power in preparation for provocation & contingency, especially over the area where the above countries have claimed the marine sovereignty and jurisdiction. This paper analyzes the validity of establishment and operation of Air Defense Identification Zone(ADIZ) in Northeast Asia, researching the legal feasibility of the military activities, the freedom of navigation and overflight in Economic Exclusive Zone(EEZ) and near high seas in the point of view of the international laws, national security and general practice.