This chapter presents a comprehensive examination of the functions of sentence-middle modal particles. In Chinese grammar, there is no analysis of the sentential information structure. The use of “translocation” to emphasize the focus information and the use of the modal particle to weaken the secondary information are the speaker's means of expression corresponding respectively to the dialogic and the narrative style, and to non-canonical and canonical sentences. Although the opposition of “subject-predicate” and “topic-comment” have certain correspondence with “old information-new information,” they cannot accurately reflect the information structure of the sentence. The textual, topical and modal components (respectively referred to as the textual, topical and interpersonal themes in the analysis of thematic structure in spoken Pekingese) can sometimes co-occur in one sentence. Historically the sentence-middle modal particles in spoken modern Chinese have evolved from sentence-final modal particles, during the process of which their questioning and exclamatory modal meanings have been gradually bleached to varying extents.