Abstract
This paper uses the opening speech given by president Obama at a prime time news conference commemorating his first 100th day in office as the sample and tries to explore how interpersonal meaning is achieved from the perspective of Functional Grammar and with the focus on mood, modal auxiliary, personal pronouns in pronoun system, and tense shift. The finding shows that Obama makes full use of the language to achieve his political purpose in his speech by using different devices to fulfill interpersonal meaning.