This paper reviews Chiang Kai-shek"s plan and will to regain the mainland before and after the outbreak of the Korean War in 1950. Chiang Kai-shek, who moved to Taiwan after the defeat of the civil war, conceived a plan, that is called “Return to Mainland” in order to stabilize the regime. After losing Mainland, he needs to retaliate to consolidate internal unity.<BR> To Carry out a Plan “Return to Mainland”, Chiang Kai-shek must first solve the problems of US military support and participation. Chiang Kai-shek expected South Korea to play an important role here.<BR> At that time, the United States insisted on retreating from Asian issues as much as possible. Therefore, Chiang Kai-shek believed that the United States would intervene only if there were disputes in Asia. In Chiang Kai-shek’s view, the region with the greatest possibility of conflict in Asia was the Korean Peninsula. In addition, Shao Yu-lin made a suggestion that Korea is the most appropriate place to collect information and supplies for the “Return to Mainland”. Chiang Kai-shek hopes that will increase tensions on the Korean Peninsula, that he will be able to participate actively in the issue and will expand the anti-Communist front from the Korean Peninsula to mainland China.<BR> Although the crisis on the Korean Peninsula that the Nationalist government expected broke out, that is, the Korean War, but Chiang Kai-shek was unable to participate in the crisis on the Korean Peninsula and to link it to the plan “Return to Mainland”. Chiang Kai-shek conveyed to South Korea and the U.S. the intention to dispatch troops, but the U.S. refused to accept Chiang Kai-shek"s offer, fearing the intervention of the Chinese Communists. Chiang Kai-shek believed that in order to achieve a plan to counter-attack on the Mainland, co-operation among the anti-Communist camp must be established. Chiang Kai-shek applied this idea to the American anti-Communist, MacArthur.<BR> At the end of July 1950, MacArthur visited Taiwan, showed a very friendly attitude towards Chiang Kai-shek, and promised the National Government to provide assistance. But the United States had no intention of supporting Chiang Kai-shek"s “Return to Mainland” plan. Although MacArthur provided Chiang Kai-shek with promised aid, it was not enough to attack the mainland.<BR> In the late 1950s, what changed the situation on the Korean Peninsula was the dispatch of troops by the CCP. The U.S. is opposed to the dispatch of troops by KMT troops in fear of the intervention of the Chinese Communist forces, but in the end the Chinese Communist forces intervened in the Korean War.<BR> After the Chinese military intervened in the Korean War, Chiang Kai-shek also mentioned “Return to Mainland”, but his rhetoric changed. The reason was that the U.S. supported Army Commander-in-Chief Sun Li-jen rather than itself.<BR> In early 1950, Chiang Kai-shek proposed a plan “Return to Mainland” in order to stabilize his regime. But after the Chinese Communists entered the war, if they send KMT troops to South Korea or send to the mainland, the United States had to worry about the “defense of Taiwan”. And the United States believed that even if a second front was opened, its commander would not need to be Chiang Kai-shek.<BR> Finally, as President Truman opposed the intervention of the military, domestic discussions about the use of the military were suspended. Chiang Kai-shek also did not advocate active participation in the Korean War, so neither the Korean War nor Chiang Kai-shek"s “Return to Mainland” further link up.