The macro constructs of disciplinary English consist disciplinary contents and English language, whose interface and fusion mechanism at the micro-level are explored hereby from the “event domain” : English language constructs disciplinary contents into knowledge in an academic way, which is held in this paper to be the substantive cross-interface within disciplinary English. Resting upon this interface are layer of grammatical construction, layer of disciplinary knowledge construction and layer of disciplinary feature construction. Disciplinary contents are constructed through English language into knowledge at each of the three layers that constitute a three- dimensional construction mechanism of organic fusion in general.