The present paper revisits a long-standing controversial issue in Chinese grammar — the passive voice — from a systemic functional approach. This study examines how the ba- and bei-constructions control the flow of information in text and shows that they are textually motivated. It argues, by differentiating the bei-construction from the OSV structure, and the ba-construction from the SOV and SVO structures, that the two constructions are not options of THEME, but form a separate level within the grammar. It then describes the system of VOICE in the language. Furthermore, facing the increasing productivity of the ba- and bei-constructions in process types other than transitive material processes, this study examines this trend of increasing productivity.