Halliday pointed out: People use their interpersonal functions to express their opinions, attitudes, identities and intentions, establishing and maintaining a specific society and interpersonal relationship. The graduation ceremony speech is a kind of public speech and one of the important components of campus cultures. Scholars from different fields have studied it from different perspectives. However, these studies focus on the analysis of speech skills, text structure or language style and those are less interpreted from the perspective of language interpersonal meta-function theory. The author attempts to use the interpersonal meta-function theory to explore the interpersonal meta-function and its implementation in the speech of Zuckerberg’s Harvard University graduation ceremony. The study found that: first, the statement tone, interrogative tone and command tone are the types of tone in interpersonal function in the graduation ceremony speech, but the main form of realization is the statement tone. Second, at the graduation ceremony, speakers tend to use median and low-value modal words, and rarely use high-value modal words as the use of high-modality words imposes obligations and pressure on the audience, and the use of median and low values makes the audience more acceptable and more convincing.
