Although Trump portrayed the Islamic Republic of Iran as a threat to US security and interests and succeeded in securitization of the Islamic Republic of Iran within the United States, he failed to introduce the Islamic Republic of Iran as a threat to international security at the global community level. For example, at a meeting of the UN Security Council on August 14, 2020, only two of the 15 members of the UN Security Council adopted a resolution proposed by the United States that would lift the arms Sanction imposed on Iran, they voted in favor. Whereas if Trump had succeeded in portraying the Islamic Republic of Iran as a threat to international security, all or a majority of members of the UN Security Council would have voted in favor of the resolution. Although various theoretical frameworks can be used to explain this issue, this research uses the concept of "Macrosecuritisation" proposed by the Copenhagen School that is part of the theory of "securitization" and trying to investigate the causes of this issue. Therefore, this study seeks to answer the main question: "What are the reasons for the Failure of Trump's Securitizing Speech-act, and introduction of the Islamic Republic of Iran as a threat to international security? " present the hypothesis and mentions five reasons. the hypothesis of this Research is: Trump's failure to Macrosecuritisation of the Islamic Republic of Iran stems from five factors: 1) the inability to present the Islamic Republic as a macro-threat to the macro security Referent Object, that Here, the world community (or at least the Western bloc), and to be more precise, disregards to the external aspect of the facilitating conditions of Securitization,2) the lack of a unity of negatives as one of the success factors of a Macrosecuritisation,3) Lack of persuasion of the audience and, more precisely, inability to turn ordinary audiences into supportive audiences, Due to the low social capital of the Securitizing Actor (Trump) in the international community,4) Lack of adding a universal dimension to Trump's Securitizing Speech-act of the Islamic Republic of Iran,5) Lack of selection of appropriate watch words and terms that can be invoked to move specific issues into the realm of securitization without elaborate arguments about the securitization of the specific case. This research can be considered as a qualitative-quantitative research in which qualitative tools such as Content Analysis Method of eight Trump's speeches / comments / statements and quantitative tools such as the results of polls of reputable Western Institute are used.