This research takes the initiative to achieve objective identification of semantic waves in disciplinary discourse from the perspective of fractal elements through corpus-assisted discourse analysis. This research will contrastively analyze different expression of the shared semantics between scientific discourse and popular science discourse mainly in terms of Systemic Functional Grammar (SFG), and then rank the fractal elements to form an objective scale based on their strengths of SD/SG. The scale built through the integration of corpus discourse analysis and review of previous relevant theoretical literature realizes the objective construal of the dynamic change of SD/SG as discourse unfolds, extending the employment of semantic wave in exploring the scientific knowledge building in discourse and developing semantic wave by further integrating this knowledge building theory with Systemic Functional Linguistics (SFG).