Modal discourse markers play an important role in language communication,and the analysis of modal discourse markers is in full swing,but a large amount of analysis focuses on written texts,such as academic writing or celebrity speeches,and few studies on the actual use of L2 learners.This study is conducted based on the theoretical framework of interpersonal meaning in Halliday’s functional grammar,and analyzes the dialogue in the multi-modal spoken corpus of science and engineering college students from the perspective of modality,hoping to provide reference for L2 learning and teaching.