The Origins of the Korean War, especially their role of and interrelations among Stalin, Mao Zedong, Kim Ill-Sung has been attracted by many researchers. Because, above all, it is important to understand the characters and historic implications of the Cold War as well as the Korean War. Generally, a great of scholars have accepted that Stalin's desire for world revolution and the Soviet Union's traditional expansionism ignited the beginning of the Korean War. And, it has become a natural conclusion that Stalin's aim in Korean War was the exclusive control of Korea as a whole. In fact, they have evidenced by a lots new historical materials after the death of the Old Socialist Camp. The established scholarships have many merits, but also the false to strain the reality. The aim of this present study is to examine why stalin approved Kim Ill-Sung's appeal to reunify Korean peninsular by military means. To effectively reach that aim, it is preconditioned that the dialectics of centripetal and centrifugal power was the operating mechanism of the Cold War, the letter was prevailing. In other words, The US and the USSR hope to get control of the Inside, not expand forward the Outside of their sphere of power. This theory is applied to Stalin's Green Signal to the Korean War. The following is the results of this study. Firstly, at the end of 1949 the success of Chines Revolution and beginning of 1950 the conclusion of Sino-Soviet Alliance gave a burden to Stalin, not him some confidence about Asian Revolution. With the rise of new China, the international political Status of Stalin and the USSR was increasingly to challenged. Stalin and the USSR have a new threat, Stalin will never accept it. Secondly, the North Korean Leader, Kim Ill-Sung insisted steadfastly the reunification of two Korea. For Stalin, Kim' suggestion was a kind of pressure. As a revolutionary and revolutional world leadership, Stalin had no choice but to approve Kim's appeal to a revolutional war, fearing a American response. Thirdly, though reluctantly, Stalin decided the North Korean invasion of South. Stalin's logics and conditions of Korean War were, first of all, the US will intervene Korean peninsular situation. Stalin hope to make China directly fight with the US. That was a device to weak China and draw to its dependence on the USSR. The anticipated Kim Ill-Sung' failure to achieve an unification will justify Stalin's assessing the US intervention and is able to pass Mao and Kim the responsibility for miscalculation of it. Fourthly, Stalin had not the intention and capability to fight the US, and desire to notify the US his real thoughts to not challenge the super-great power. Therefore, Stalin's seemingly dual attitudes was the presentation of his prudently calculated strategy, not his opportunity. To sum it up, Stalin hope to make China directly fight with th US. It was a device to weak China and draw to its dependence on the USSR. And, Stalin will justify his rightness of assessing the US intervention and pass Mao and Kim the responsibility for miscalculation of it. finally, Stalin hope to notify the US his not intent to fight with it. Therefore, Stalin's choice of the Korean War was a strategic politics considered a changed situation of Asia and the mechanism of the Cold War, not to get control of Korea as a whole.