The State of the Union Address refers to the annual report of the sitting president to congress, which is a representative political discourse. It mainly deals with the major issues in the United States that year, both at home and abroad and the policy measures are to be taken by the government. Transitivity system is a semantic system of ideational function and plays a very important role in discourse analysis. It expresses people’s experience of the real world and the inner world in a number of processes and indicates the participants and environmental components involved in the process. This paper takes the transitivity system in Halliday’s ideational functions as the theoretical framework and US President Donald Trump’s 2018 State of the Union Address as the language material. It mainly analyzes the transitivity process, main participants, and environmental elements embodied in the speech and makes statistics on their distribution, and finally obtaining the reasons for the distribution is that Trump wants to get support by proving his ability.