After the Post-Cold War Era. U.S. has concerned much about Asia-Pacific region. There were about 100,000 U.S. military personnel in this region shaping the security environment in order to maintain America's Asia Pacific strategy interests. After Iraqi War, U.S. senior defense officials has expressed different opinions on global force posture. which has produced dramatic thoughts about the transformation of American overseas military presence strategy in Asia-Pacific. The key point of this report is to analyze the measures that U.S. will take to face the East Asia security situation, In this report, will also discuss China's strategic measures in response to America's policy adjustment. and how these transformations shall have impacts on the security situation of Taiwan Strait. At the part of conclusion and suggestion, its order to preserve Taiwan's survival development, there will some defense policy recommendations.