With its national strength, the United States is, more often than not, a major State initiating the making of important international multilateral treaties and shaping the final outcome by wielding its influence in the negotiation processes. Nevertheless, three major international multilateral treaties concluded in three different domains all appear the same situation in which the U.S. participated actively in the negotiations but ended up rejecting to sign or ratify due to their inconformities with American ¡§national interests.¡¨ The purpose of this thesis is to examine the American proposals and interventions made in the negotiating processes of three important international multilateral treaties, i.e., the United Nations Convention on the Law of the Sea, Kyoto Protocol and Rome Statute of the International Criminal Court, so as to understand American negotiation stances as well as the issues to which the U.S. attached importance to and the derive the substantive contents of the ¡§national interests¡¨ that the U.S. held dear. Furthermore, this thesis takes one step further to analyze who were the actors that shaped and defined the ¡§national interests¡¨ which the U.S. valued and held tight.