Abstract: The norm of explicitation and implicitation has long been a source of wider attention in translation studies. This paper, setting off from Systemic Functional Linguistics, sees explicitation and implicitation as semantic choices of a translator or interpreter and proposes a tripartite model the norm, namely, ideational, interpersonal and textual. In addition, the paper presents a discussion of actualization of the norm with discourse examples from a Chinese Premier's Press Conference. The study expands the conceptual connotation of explicitation and implicitation and may shed light on empirical research in future.