|President Franklin Roosevelt of the United States, conceiving China's cooperation with the Allied Powers and contribution to the campaign against the Axis during the Second World War, proposed a new relationship in which the United States invited China to be a key member cooperating for the postwar international world order. When Harry Truman took power, the situations in Easter Europe and China became complicated when Soviet wielding Yalta agreement. Easter European countries were occupied by the Soviets, satellite states established, China was usurped by the communists after a bitter civil war. The Republic of China (ROC), known as the Nationalists, fled to Taiwan after defeat, and the communists declared the establishment of government of the People's Republic China (PRC) in October 1949. The United States had to encounter difficulties, i.e., how to deal with the newly erected PRC and to evaluate its role in the East Asian international relations. The Truman government did not like Chiang Kai-shek. Truman went further to release a White Paper proposing a ”let the dust be settled” policy, meant that Washington would eventually consider building up formal relations with the PRC at the expense of Taiwan. Not until the Korean War in June 1950, did the Truman Administration feel the North Korean attack as a portion of the international communist expansion. Truman thought that East Asia may be similar to East Europe unless the North Korean invasion vehemently deterred. In the meantime, the United States abruptly changed its policy toward Taiwan, when Truman constructed a containment policy including the PRC and revived support for Taiwan. This article tries to vision the change, characteristics, and impacts of the U.S.' policy toward Taiwan during the Korean War by covering the shifting international relations and the development of the regional conflict in East Asia, and the internal politics of the United States. The main themes of this article will be as follows: the United States did not offer enough concern to Korea or Taiwan until the Korean War occurred; American China policy was intertwined with the U.S.-Soviet Cold War since then; while the PRC was isolated from the international community because of China's intervention into the Korean War, the ROC earned a chance to begin economic develop and national security. The United States, however, would in the meantime appreciate dialogues with the PRC after the Korean War. The protracted dialogues between Washington and Beijing finally resulted in diplomatic normalization some twenty years later.