Abstract Securitization is the core theory of the Copenhagen school, of which the main argument is that security is a social construction between “speech act” agents rather than objectively established, and any problem could be subjectively constructed as a security problem. Securitization includes three procedures:discursive salience and securitization initiation, discursive framing and securitization communication, as well as discursive positioning and securitization measure. In recent years, the U.S. has attempted to propose freedom of navigation (FON) in the South China Sea as a security issue. As the securitization agent, the U.S. intends to highlight the threats to FON in the south china sea. At the same time, it takes advantage of the media reports to exaggerate the so⁃called security threats and asserts FON as its national interests. Since then, the U.S. has taken measures to deal with the threats, and FON in the South China Sea has rapidly become the focus of China⁃U.S. relations as well as the international community. The success of the U.S. securitization depends on its strong capabilities of communication and mobilization, as well as its unique domestic institutional advantages, and it takes advantage of concerns of the countries involved in the South China Sea issue confronted with a security dilemma. In view of this, China needs to make efforts in de⁃securitization, rendering the U.S. securitization only a subjective intention.