Abstract:The notion of semantic wave is a growing focus between Systemic Functional Linguistics and Legitimation Code Theory. It is found that few studies are concerned about an explicit objective identification of semantic waves, particularly about how semantic waves are supposed to be identified objectively and judged explicitly in addition to its specific semiotic functions. This paper tries to construct an explicit and objective framework for semantic wave identification in terms of the rhetorical units of a text, and further explore its semiotic mediating functions of approximation, technicalization and legitimation so as to make an objective interpretation for its appliable and legitimate status and develop a cutting approach for powerful knowledge building in the disciplinary text of bilingual science.