本文聚焦在胡適與蔣介石這兩位歷史人物於1948至1962年間的互動。作為近代中國重要學術領導人物的胡適，在1949至1958年間寓居美國，但仍關心臺灣時事與發展狀況，這可說是他生涯轉捩點。他和黨政軍最高領導人、亟欲透過軍事反攻大陸以雪恥的蔣介石，彼此因為反共而有共同合作的理由。但透過近年新出現的相關人物日記作觀察，則可知彼此性格及思想差異，從未因為彼此互動而消失。因此本文即分下列階段：依違離合、雪中送炭、緊張關係推升、衝突至破裂，以論述胡適與蔣介石之互動關係。蔣介石與胡適在外在環境緊迫時，確曾給予彼此支持，但最終也因為政治理念不同，胡適堅持憲政及自由人權主張，於出版法修正案、針對總統三連任問題、雷震案等事件導致胡、蔣之對立。

This essay will discuss interactions between the two unprecedented historical figures-Hu Shih and Chiang Kai-shek from 1948 to 1962. As one of the most important Chinese leading scholars, if not the most, Hu stayed in the United States from 1949 to 1958, with a very serious eye on the political development in Taiwan, as this was the most crucial turning point in his later years or life. Chiang Kai-shek, who was very eager to use force, if necessary, to recover Mainland China to revenge his disgrace at the hands of the CCP, had ample reasons to cooperate with Hu for mutual and joint anticommunism both in China and in the world. As soon as we are now being given the opportunity to study respectively the diaries of these two preeminent figures in China, we can immediately understand the differences between them as regards their personalities and political thoughts, which resulted in their eventual parting of ways of sort. This essay lists roughly four-stages in the unfolding of their interactions: first, there was separation then cooperation between them in various areas; secondly, there was timely help rendered by Hu; thirdly, there were conflicts in acceleration; and finally, there was almost a complete break in their interactions. In the study, it was found that when both Hu and Chiang were faced with serious external stresses, they would support each other. But as history shows, their differences in the matters of political thoughts, publications law amendments, and Chiang's third term of presidency problem and the Lei Chen case did finally make their further and future interactions unprofitable or even impossible.