Abstract: Expanding the research on Modality, Systemic Functional Linguistics distinguishes two basic types of Modality, namely Modalization and Modulation, in terms of different speech roles involved.With Modulation, it corresponds to Deontic Modality defined in logic, and this paper is firstly to review the discussions of this type of Modality within SFL, and then, combined with Bakhtin's Heteroglossia, to carry out an analysis of Deontic Modality in 3 editorials on the Copenhagen Climate Meeting, with the focus on the construal of attitude and stance, the functional tenor of editorials.