China obtains the best security environment ever as the Cold War ended. Its economy continues to grow. China¡¦s rise becomes a reality. Along with China's enhancement on economy and military strengths, Beijing shows more confidence in dealing with international affairs. Zhongnanhai leaders keep stressing that China will strive for an international environment in favor of peace and development, and expressing to the U.S. that China is willing to be cooperative on regional and international issues, which wins praise from President Bush. China and the U.S. both carry on some strategic adjustment. Moreover, President Bush becomes the first U.S. president who visited China three times in its two tenures in office. President Bush and Hu Jintao have gradually established personal friendship. Chinese leaders have long regarded the pursuing of country¡¦s unification as the most important and prior political goal. In China's leadership, both reformists and hardliners take ¡§Taiwan issue" as sovereignty matter, the core interest of China¡¦s national security. Jiang Zemin used to emphasize that ¡§Taiwan issue is the most sensitive and most crucial issue in Sino-U.S. relations.¡¨ Every time when Hu Jintao met with President Bush, Hu applauded the U.S.¡¦s commitments on ¡§One-China¡¨ policy, three Joint Communiques, and ¡§opposition¡¨ of Taiwan independence. Bush administration¡¦s policies toward Taiwan Strait security have also shifted from strategic ambiguity to strategic clarity gradually. China-U.S. relationship has been promoted to its best status in second half of 2003 due to the intensification of international anti-terrorism cooperation and Beijing¡¦s role in hosting Six Party Talks. The atmosphere of Taiwan-U.S. relationship, however, has been not so good since President Chen Shui-bian¡¦s second term because Taiwan repeatedly pushes Washington D.C.¡¦s bottom lines. Bush administration made several friendly decisions toward Taiwan in its early stage after resuming powers, including providing better treatments for Taiwan senior leaders when they visited or transited the U.S. But when President Bush said he would do ¡§whatever it takes to defend Taiwan¡¨ in early 2001, the White House and U.S. State Department quickly repeated that the U.S. policies remain unchanged. It shows that the risks for military conflict in Taiwan Strait are high and that the U.S. does not want Taiwan to have too much expectation. Washington, D.C. would avoid getting into military conflicts in Taiwan Strait for its own interests. In addition, Bush administration continues to aware Taiwan that the U.S. and Taiwan could cooperate in some security affairs, but the U.S., out of its strategy consideration and moral responsibility, would be the sole country which could assist democratic Taiwan. This dissertation would mainly explore China¡¦s rise, and in this presupposition, the Bush Administration¡¦s Policies on Cross-Strait Relations. The dissertation comprises 7 chapters. Besides introduction and conclusion in the first and the seventh chapter respectively, the second chapter would study China¡¦s rise and its challenges to the U.S. and the U.S.¡¦s security strategies in Asia-Pacific region, while the third chapter discussing Bush administration¡¦s policies toward China, the fourth chapter analyzing China¡¦s policies toward Bush administration, the fifth chapter looking into the U.S. factors in China¡¦s policies toward Taiwan, and the sixth chapter reviewing cross-strait relations during Bush administration. To sum up, Bush administration emphasizes stability across the Taiwan Strait. Neither side of the Taiwan Strait can take unilateral actions to change the status quo, which is defined by the U.S., and the solution of cross-strait issues must be through peaceful ways. To respond of China¡¦s rise, the U.S. continues to underline its relationship with allies in Asia-Pacific. At the same time, Bush administration makes more concrete steps in strengthening U.S.-Taiwan military cooperation, while U.S.-China military exchanges in progress but with limitation.