Abstract: The study of discourse subjectivity focuses on the dynamic construction of speakers’ attitudinal stances in discursive communication, highlighting his consciousness of self in producing discourses, which has become a central concern in linguistic research. Speakers strategically employ linguistic choices to engage in and expressing attitudinal evaluation, manifesting the construction of discourse subjectivity. While the engagement system proposed by Martin et al. (2005) emphasizes positioning, it inadequately addresses speakers' subjective consciousness. This paper reconstructs the engagement system framework and investigates the construction of discourse subjectivity from the perspective of speaker engagement. First, a new engagement system is worked out, which includes two aspects of engaging mode and degree, subcategorizing such three dimensions as voice, position and engagement values. Secondly, based on this system, it studies how discourse subjectivity is collaboratively constructed in terms of discourse perspective, discourse position and dialogue force. Finally, the dynamic construction of discourse subjectivity and its implications for further research in this field are discussed. In summary, this study explores the dynamic construction of discourse subjectivity from the perspective of discourse semantics, with a view to enhancing the study of discourse subjectivity in the future.