有鑑於東亞日益嚴峻之安全挑戰，美國、日本，和韓國之間的三方同盟合作備受期待，卻也同時面臨難以解決之阻礙。無論是在南海，中國持續性的相關侵略行動及建設，或是在東北亞的北韓導彈及核威脅，美、日、韓三國在面臨共同威脅的同時，在促進共同利益的基礎上，一個更為一致且具體的應對政策顯得至關重要，三方同盟的可行性乍看下也似乎相當高。然而，由於日本和韓國之間的歷史問題懸而未決，雙方長期缺乏互信基礎，因此日韓關係的改善並不順遂，也造成三方安全同盟於一定程度上之窒礙難行。本文期冀能藉由結構現實主義分析國際層次面之結構因素，以及建構主義探究國家內部之歷史認同與領導人理念，以結合此兩種途徑，因此將嘗試琢研兩大理論間之互動觀點以探討美—日—韓三方安全同盟的可行性與有限性。 In view of the increasingly severe security challenges in East Asia, the trilateral alliance among the United States, Japan, and South Korea is highly anticipated, but it also faces impenetrable barriers, challenges and obstacles to embrace and overcome. Whether in the South China Sea, China’s continuing aggressive actions, or North Korea’s missiles and nuclear threat, the United States, Japan, and South Korea face common threats while promoting common interests. In this regard, the viability of the three-party alliances seems quite high. Nevertheless, due to the unresolved historical issues between Japan and South Korea, and the long-term lack of mutual trust between the two sides, the improvement of relation between Japan and South Korea is not smooth, and it has also caused the trilateral alliance to hamper the development to a certain extent. Owing to that, I try to study the interactive perspectives between the two theories by analyzing structural factors at the international level through structural realism and constructivism to explore the colloective identities and ideas within South Korea to combine these two approaches and thus exploring the feasibility and limitations of the U.S.-Japan-South Korea trilateral alliance.